How Irregularities in Electron Density Perturb Satellite Navigation Systems
By the Satellite-Based Augmentation Systems Ionospheric Working Group
INNOVATION INSIGHTS by Richard Langley
THE IONOSPHERE. I first became aware of its existence when I was 14. I had received a shortwave radio kit for Christmas and after a couple of days of soldering and stringing a temporary antenna around my bedroom, joined the many other “geeks” of my generation in the fascinating (and educational) hobby of shortwave listening. I avidly read Popular Electronics and Electronics Illustrated to learn how shortwave broadcasting worked and even attempted to follow a course on radio-wave propagation offered by a hobbyist program on Radio Nederland. Later on, a graduate course in planetary atmospheres improved my understanding.
The propagation of shortwave (also known as high frequency or HF) signals depends on the ionosphere. Transmitted signals are refracted or bent as they experience the increasing density of the free electrons that make up the ionosphere. Effectively, the signals are “bounced” off the ionosphere to reach their destination.
At higher frequencies, such as those used by GPS and the other global navigation satellite systems (GNSS), radio signals pass through the ionosphere but the medium takes a toll. The principal effect is a delay in the arrival of the modulated component of the signal (from which pseudorange measurements are made) and an advance in the phase of the signal’s carrier (affecting the carrier-phase measurements). The spatial and temporal variability of the ionosphere is not predictable with much accuracy (especially when disturbed by space weather events), so neither is the delay/advance effect. However, the ionosphere is a dispersive medium, which means that by combining measurements on two transmitted GNSS satellite frequencies, the effect can be almost entirely removed. Similarly, a dual-frequency ground-based monitoring network can map the effect in real time and transmit accurate corrections to single-frequency GNSS users. This is the approach followed by the satellite-based augmentation systems such as the Federal Aviation Administration’s Wide Area Augmentation System.
But there is another ionospheric effect that can bedevil GNSS: scintillations. Scintillations are rapid fluctuations in the amplitude and phase of radio 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 or tracking or in causing problems for the receiver’s phase lock loop resulting in many cycle slips.
In this month’s column, the international Satellite-Based Augmentation Systems Ionospheric Working Group presents an abridged version of their recently completed white paper on the effect of ionospheric scintillations on GNSS and the associated augmentation systems.
The ionosphere is a highly variable and complex physical system. It is produced by ionizing radiation from the sun and controlled by chemical interactions and transport by diffusion and neutral wind. Generally, the region between 250 and 400 kilometers above the Earth’s surface, known as the F-region of the ionosphere, contains the greatest concentration of free electrons. At times, the F-region of the ionosphere becomes disturbed, and small-scale irregularities develop. When sufficiently intense, these irregularities scatter radio waves and generate rapid fluctuations (or scintillation) in the amplitude and phase of radio signals. Amplitude scintillation, or short-term fading, can be so severe that signal levels drop below a GPS receiver’s lock threshold, requiring the receiver to attempt reacquisition of the satellite signal. Phase scintillation, characterized by rapid carrier-phase changes, can produce cycle slips and sometimes challenge a receiver’s ability to hold lock on a signal. The impacts of scintillation cannot be mitigated by the same dual-frequency technique that is effective at mitigating the ionospheric delay. For these reasons, ionospheric scintillation is one of the most potentially significant threats for GPS and other global navigation satellite systems (GNSS).
Scintillation activity is most severe and frequent in and around the equatorial regions, particularly in the hours just after sunset. In high latitude regions, scintillation is frequent but less severe in magnitude than that of the equatorial regions. Scintillation is rarely experienced in the mid-latitude regions. However, it can limit dual-frequency GNSS operation during intense magnetic storm periods when the geophysical environment is temporarily altered and high latitude phenomena are extended into the mid-latitudes. To determine the impact of scintillation on GNSS systems, it is important to clearly understand the location, magnitude and frequency of occurrence of scintillation effects.
This article describes scintillation and illustrates its potential effects on GNSS. It is based on a white paper put together by the international Satellite-Based Augmentation Systems (SBAS) Ionospheric Working Group (see Further Reading).
Scintillation Phenomena
Fortunately, many of the important characteristics of scintillation are already well known.
Worldwide Characteristics. Many studies have shown that scintillation activity varies with operating frequency, geographic location, local time, season, magnetic activity, and the 11-year solar cycle. FIGURE 1 shows a map indicating how scintillation activity varies with geographic location. The Earth’s magnetic field has a major influence on the occurrence of scintillation and regions of the globe with similar scintillation characteristics are aligned with the magnetic poles and associated magnetic equator. The regions located approximately 15° north and south of the magnetic equator (shown in red) are referred to as the equatorial anomaly. These regions experience the most significant activity including deep signal fades that can cause a GNSS receiver to briefly lose track of one or more satellite signals. Less intense fades are experienced near the magnetic equator (shown as a narrow yellow band in between the two red bands) and also in regions immediately to the north and south of the anomaly regions. Scintillation is more intense in the anomaly regions than at the magnetic equator because of a special situation that occurs in the equatorial ionosphere. The combination of electric and magnetic fields about the Earth cause free electrons to be lifted vertically and then diffuse northward and southward. This action reduces the ionization directly over the magnetic equator and increases the ionization over the anomaly regions. The word “anomaly” signifies that although the sun shines above the equator, the ionization attains its maximum density away from the equator.
FIGURE 1. Global occurrence characteristics of scintillation. (Figure courtesy of P. Kintner)
Low-latitude scintillation is seasonally dependent and is limited to local nighttime hours. The high-latitude region can also encounter significant signal fades. Here scintillation may also accompany the more familiar ionospheric effect of the aurora borealis (or aurora australis near the southern magnetic pole) and also localized regions of enhanced ionization referred to as polar patches. The occurrence of scintillation at auroral latitudes is strongly dependent on geomagnetic activity levels, but can occur in all seasons and is not limited to local nighttime hours. In the mid-latitude regions, scintillation activity is rare, occurring only in response to extreme levels of ionospheric storms. During these periods, the active aurora expands both poleward and equatorward, exposing the mid-latitude region to scintillation activity. In all regions, increased solar activity amplifies scintillation frequency and intensity. Scintillation effects are also a function of operating frequency, with lower signal frequencies experiencing more significant scintillation effects.
Scintillation Activity. Scintillation may accompany ionospheric behavior that causes changes in the measured range between the receiver and the satellite. Such delay effects are not discussed in detail here but are well covered in the literature and in a previous white paper by our group (see Further Reading, available online).
Amplitude scintillation can create deep signal fades that interfere with a user’s ability to receive GNSS signals. During scintillation, the ionosphere does not absorb the signal. Instead, irregularities in the index of refraction scatter the signal in random directions about the principal propagation direction. As the signal continues to propagate down to the ground, small changes in the distance of propagation along the scattered ray paths cause the signal to interfere with itself, alternately attenuating or reinforcing the signal measured by the user. The average received power is unchanged, as brief, deep fades are followed by longer, shallower enhancements.
Phase scintillation describes rapid fluctuations in the observed carrier phase obtained from the receiver’s phase lock loop. These same irregularities can cause increased phase noise, cycle slips, and even loss of lock if the phase fluctuations are too rapid for the receiver to track.
Equatorial and Low Latitude Scintillations. As illustrated in Figure 1, the regions of greatest concern are the equatorial anomaly regions. In these regions, scintillation can occur abruptly after sunset, with rapid and deep fading lasting up to several hours. As the night progresses, scintillation may become more sporadic with intervals of shallow fading. FIGURE 2 illustrates the scintillation effect with an example of intense fading of the L1 and L2 GPS signals observed in 2002, near a peak of solar activity. The observations were made at Ascension Island located in the South Atlantic Ocean under a region that has exhibited some of the most intense scintillation activity worldwide. The receiver that collected this data was one that employs a semi-codeless technique to track the L2 signal. Scintillation was observed on both the L1 and L2 frequencies with 20 dB fading on L1 and nearly 60 dB on L2 (the actual level of L2 fading is subject to uncertainty due to the limitations of semi-codeless tracking). This level of fading caused the receiver to lose lock on this signal multiple times. Signal fluctuations depicted in red indicate data samples that failed internal quality control checks and were thereby excluded from the receiver’s calculation of position. The dilution of precision (DOP), which is a measure of how pseudorange errors translate to user position errors, increased each time this occurred. In addition to the increase in DOP, elevated ranging errors are observed along the individual satellite links during scintillation.
FIGURE 2. Fading of the L1 and L2 Signals from one GPS satellite recorded from Ascension Island on March 16, 2002. Absolute power levels are arbitrary. (Figure courtesy of C. Carrano)
FIGURE 3 illustrates the relationship between amplitude and phase scintillations, also using measurements from Ascension Island. As shown in the figure, the most rapid phase changes are typically associated with the deepest signal fades (as the signal descends into the noise). Labeled on these plots are various statistics of the scintillating GPS signal: S4 is the scintillation intensity index that measures the relative magnitude of amplitude fluctuations, τI is the intensity decorrelation time, which characterizes the rate of signal fading, and σφ is the phase scintillation index, which measures the magnitude of carrier-phase fluctuations.
FIGURE 3. Intensity (top) and phase scintillations (bottom) of the GPS L1 signal recorded from Ascension Island on March 12, 2002. (Figure courtesy of C. Carrano)
The ionospheric irregularities that cause scintillation vary greatly in spatial extent and drift with the background plasma at speeds of 50 to 150 meters per second. They are characterized by a patchy pattern as illustrated by the schematic shown in FIGURE 4. The patches of irregularities cause scintillation to start and stop several times per night, as the patches move through the ray paths of the individual GPS satellite signals. In the equatorial region, large-scale irregularity patches can be as large as several hundred kilometers in the east-west direction and many times that in the north-south direction. The large-scale irregularity patches contain small-scale irregularities, as small as 1 meter, which produce scintillation. Figure 4 is an illustration of how these structures can impact GNSS positioning. Large-scale structures, such as that shown traversed by the signal from PRN 14, can also cause significant variation in ionospheric delay and a loss of lock on a signal. Smaller structures, such as those shown traversed by PRNs 1, 21, and 6, are less likely to cause loss of the signal, but still can affect the integrity of the signal by producing ranging errors. Finally, due to the patchy nature of irregularity structures, PRNs 12 and 4 could remain unaffected as shown. Since GNSS navigation solutions require valid ranging measurements to at least four satellites, the loss of a sufficiently large number of satellite links has the potential to adversely affect system performance.
FIGURE 4. Schematic of the varying effects of scintillation on GPS.
FIGURE 5 illustrates the local time variation of scintillations. As can be seen, GPS scintillations generally occur shortly after sunset and may persist until just after local midnight. After midnight, the level of ionization in the ionosphere is generally too low to support scintillation at GNSS frequencies. This plot has been obtained by cumulating, then averaging, all scintillation events at one location over one year corresponding to low solar activity. For a high solar activity year, the same local time behavior is expected, with a higher level of scintillations.
FIGURE 5. Local time distribution of scintillation events from June 2006 to July 2007 (in 6 minute intervals). (Figure courtesy of Y. Béniguel)
FIGURE 6 (top panel) shows the variation of the monthly occurrence of scintillation during the pre-midnight hours at Ascension Island. The scintillation data was acquired by the use of Inmarsat geostationary satellite transmissions at 1537 MHz (near the GNSS L1 band). The scintillation occurrence is illustrated for three levels of signal fading, namely, > 20 dB (red), > 10 dB (yellow), and > 6 dB (green). The bottom panel shows the monthly sunspot number, which correlates with solar activity and indicates that the study was performed during the years 1991 to 2000, extending from the peak of solar cycle 22 to the peak of solar cycle 23. Note that there is an increase in scintillation activity during the solar maximum periods, and there exists a consistent seasonal variation that shows the presence of scintillation in all seasons except the May-July period. This seasonal pattern is observed from South American longitudes through Africa to the Near East. Contrary to this, in the Pacific sector, scintillations are observed in all seasons except the November-January period. Since the frequency of 1537 MHz is close to the L1 frequencies of GPS and other GNSS including GLONASS and Galileo, we may use Figure 6 to anticipate the variation of GNSS scintillation as a function of season and solar cycle. Indeed, in the equatorial region during the upcoming solar maximum period in 2012-2013, we should expect GNSS receivers to experience signal fades exceeding 20 dB, twenty percent of the time between sunset and midnight during the equinoctial periods.
FIGURE 6. Frequency of occurrence of scintillation fading depths at Ascension Island versus season and solar activity levels. (Figure courtesy of P. Doherty)
High Latitude Scintillation. At high latitudes, the ionosphere is controlled by complex processes arising from the interaction of the Earth’s magnetic field with the solar wind and the interplanetary magnetic field. The central polar region (higher than 75° magnetic latitude) is surrounded by a ring of increased ionospheric activity called the auroral oval. At night, energetic particles, trapped by magnetic field lines, are precipitated into the auroral oval and irregularities of electron density are formed that cause scintillation of satellite signals. A limited region in the dayside oval, centered closely around the direction to the sun, often receives irregular ionization from mid-latitudes. As such, scintillation of satellite signals is also encountered in the dayside oval, near this region called the cusp.
When the interplanetary magnetic field is aligned oppositely to the Earth’s magnetic field, ionization from the mid-latitude ionosphere enters the polar cap through the cusp and polar cap patches of enhanced ionization are formed. The polar cap patches develop irregularities as they convect from the dayside cusp through the polar cap to the night-side oval. During local winter, there is no solar radiation to ionize the atmosphere over the polar cap but the convected ionization from the mid-latitudes forms the polar ionosphere. The structured polar cap patches can cause intense satellite scintillation at very high and ultra-high frequencies. However, the ionization density at high latitudes is less than that in the equatorial region and, as such, GPS receivers, for example, encounter only about 10 dB scintillations in contrast to 20-30 dB scintillations in the equatorial region.
FIGURE 7 shows the seasonal and solar cycle variation of 244-MHz scintillations in the central polar cap at Thule, Greenland. The data was recorded from a satellite that could be viewed at high elevation angles from Thule. It shows that scintillation increases during the solar maximum period and that there is a consistent seasonal variation with minimum activity during the local summer when the presence of solar radiation for about 24 hours per day smoothes out the irregularities.
FIGURE 7. Variation of 244-MHz scintillations at Thule, Greenland with season and solar cycle. (Figure courtesy of P. Doherty)
The irregularities move at speeds up to ten times larger in the polar regions as compared to the equatorial region. This means that larger sized structures in the polar ionosphere can create phase scintillation and that the magnitude of the phase scintillation can be much stronger. Large and rapid phase variations at high latitudes will cause a Doppler frequency shift in the GNSS signals which may exceed the phase lock loop bandwidth, resulting in a loss of lock and an outage in GNSS receivers.
As an example, on the night of November 7–8, 2004, there was a very large auroral event, known as a substorm. This event resulted in very bright aurora and, coincident with a particularly intense auroral arc, there were several disruptions to GPS monitoring over the region of Northern Scandinavia. In addition to intermittent losses of lock on several GPS receivers and to phase scintillation, there was a significant amplitude scintillation event. This event has been shown to be very closely associated with particle ionization at around 100 kilometers altitude during an auroral arc event. While it is known that substorms are common events, further studies are still required to see whether other similar events are problematic for GNSS operations at high latitudes.
Scintillation Effects
We had mentioned earlier that the mid-latitude ionosphere is normally benign. However, during intense magnetic storms, the mid-latitude ionosphere can be strongly disturbed and satellite communication and GNSS navigation systems operating in this region can be very stressed. During such events, the auroral oval will extend towards the equator and the anomaly regions may extend towards the poles, extending the scintillation phenomena more typically associated with those regions into mid-latitudes.
An example of intense GPS scintillations measured at mid-latitudes (New York) is shown in FIGURE 8. This event was associated with the intense magnetic storm observed on September 26, 2001, during which the auroral region had expanded equatorward to encompass much of the continental U.S. This level of signal fading was sufficient to cause loss of lock on the L1 signal, which is relatively rare. The L2 signal can be much more susceptible to disruption due to scintillation during intense storms, both because the scintillation itself is stronger at lower frequencies and also because semi-codeless tracking techniques are less robust than direct correlation as previously mentioned.
FIGURE 8. GPS scintillations observed at a mid-latitude location between 00:00 and 02:00 UT during the intense magnetic storm of September 26, 2001. (Figure courtesy of B. Ledvina)
Effects of Scintillation on GNSS and SBAS
Ionospheric scintillation affects users of GNSS in three important ways: it can degrade the quantity and quality of the user measurements; it can degrade the quantity and quality of reference station measurements; and, in the case of SBAS, it can disrupt the communication from SBAS GEOs to user receivers. As already discussed, scintillation can briefly prevent signals from being received, disrupt continuous tracking of these signals, or worsen the quality of the measurements by increasing noise and/or causing rapid phase variations. Further, it can interfere with the reception of data from the satellites, potentially leading to loss of use of the signals for extended periods. The net effect is that the system and the user may have fewer measurements, and those that remain may have larger errors. The influence of these effects depends upon the severity of the scintillation, how many components are affected, and how many remain.
Effect on User Receivers. Ionospheric scintillation can lead to loss of the GPS signals or increased noise on the remaining ones. Typically, the fade of the signal is for much less than one second, but it may take several seconds afterwards before the receiver resumes tracking and using the signal in its position estimate. Outages also affect the receiver’s ability to smooth the range measurements to reduce noise. Using the carrier-phase measurements to smooth the code substantially reduces any noise introduced. When this smoothing is interrupted due to loss of lock caused by scintillation, or is performed with scintillating carrier-phase measurements, the range measurement error due to local multipath and thermal noise could be from three to 10 times larger. Additionally, scintillation adds high frequency fluctuations to the phase measurements further hampering noise reduction.
Most often scintillation will only affect one or two satellites causing occasional outages and some increase in noise. If many well-distributed signals are available to the user, then the loss of one or two will not significantly affect the user’s overall performance and operations can continue. If the user has poor satellite coverage at the outset, then even modest scintillation levels may cause an interruption to their operation. When scintillation is very strong, then many satellites could be affected significantly. Even if the user has excellent satellite coverage, severe scintillation could interrupt service. Severe amplitude scintillation is rarely encountered outside of equatorial regions, although phase effects can be sufficiently severe at high latitudes to cause widespread losses of lock.
Effect on Reference Stations. The SBAS reference stations consist of redundant GPS receivers at precisely surveyed locations. SBAS receivers need to track two frequencies in order to separate out ionospheric effects from other error sources. Currently these receivers use the GPS L1 C/A-code signal and apply semi-codeless techniques to track the L2 P(Y) signal. Semi-codeless tracking is not as robust as either L1 C/A or future civil L5 tracking. The L2 tracking loops require a much narrower bandwidth and are heavily aided with scaled-phase information from the L1 C/A tracking loops. The net effect is that L2 tracking is much more vulnerable to phase scintillation than L1 C/A, although, because of the very narrow bandwidth, L2 tracking may be less susceptible to amplitude scintillation. Because weaker phase scintillation is more common than stronger amplitude scintillation, the L2 signal will be lost more often than L1. The SBAS reference stations must have both L1 and L2 measurements in order to generate the corrections and confidence levels that are broadcast. Severe scintillation affecting a reference station could effectively prevent several, or even all, of its measurements from contributing to the overall generation of corrections and confidences. Access to the L5 signal will reduce this vulnerability. The codes are fully available, the signal structure design is more robust, and the broadcast power is increased. L5-capable receivers will suffer fewer outages than the current L2 semi-codeless ones, however strong amplitude scintillation will still cause disruptions. Strong phase scintillation may as well.
If scintillation only affects a few satellites at a single reference station, the net impact on user performance will likely be small and regional. However, if multiple reference stations are affected by scintillation simultaneously, there could be significant and widespread impact.
Effect on Satellite Datalinks. The satellites not only provide ranging information, but also data. When scintillation causes the loss of a signal it also can cause the loss or corruption of the data bits.
Each GPS satellite broadcasts its own ephemeris information, so the loss of data on an individual satellite affects only that satellite. A greater concern is the SBAS data transmissions on GEOs. This data stream contains required information for all satellites in view including required integrity information. If the data is corrupted, all signals may be affected and loss of positioning becomes much more likely.
Mitigation Techniques. There are several actions that SBAS service providers can take to lessen the impact of scintillation. Increasing the margin of performance is chief among them. The more satellites a user has before the onset of scintillations, the more likely he will retain performance during a scintillation event. In addition, having more satellites means that a user can tolerate more noise on their measurements. Therefore, incorporating as many satellites as possible is an effective means of mitigation. GNSS constellations in addition to GPS are being developed. Including their signals into the user position solution would extend the sky coverage and improve the performance under scintillation conditions. (See the white paper for other mitigation techniques.)
Conclusions and Further Work
Ionospheric scintillations are by now a well-known phenomenon in the GNSS user community. In equatorial regions, ionospheric scintillations are a daily feature during solar maximum years. In auroral regions, ionospheric scintillations are not strongly linked to time of the day. In the mid-latitude regions, scintillations tend to be linked to ionospheric disturbances where strong total electron content gradients can be observed (ionospheric storms, strong traveling ionospheric disturbances, solar eclipses, and so on).
While the global climatic models of ionospheric scintillations can be considered satisfactory for predicting (on a statistical basis) the occurrence and intensity of scintillations, the validation of these models is suffering from the fact that at very intense levels of scintillation, even specially designed scintillation receivers are losing lock. Also, the development of models that can predict reliably the size of scintillation cells (regions of equal scintillation intensity), which allows establishing joint probabilities of losing more than one satellite simultaneously, is still ongoing.
Acknowledgments
This article is based on the paper “Effect of Ionospheric Scintillations on GNSS — A White Paper” by the SBAS-IONO Working Group.
Manufacturers
The data presented in Figure 2 was produced by an Ashtech, now Ashtech S.A.S. Z-XII GPS receiver. The data presented in Figure 5 was obtained from Javad, now Javad GNSS and Topcon Legacy GPS receivers and GPS Silicon Valley, now NovAtel GSV4004 GPS scintillation receivers. The data presented in Figure 8 was obtained from a non-commercial receiver.
The Satellite-Based Augmentation Systems Ionospheric Working Group was formed in 1999 by scientists and engineers involved with the development of the Satellite Based Augmentation Systems in an effort to better understand the effects of the ionosphere on the systems and to identify mitigation strategies. The group now consists of over 40 members worldwide.
The scintillation white paper was principally developed by Bertram Arbesser-Rastburg, Yannick Béniguel, Charles Carrano, Patricia Doherty, Bakry El-Arini, and Todd Walter with the assistance of other members of the working group.
FURTHER READING
• SBAS-IONO Working Group White Papers
Effect of Ionospheric Scintillations on GNSS – A White Paper by the Satellite-Based Augmentation Systems Ionospheric Working Group, November 2010.
Ionospheric Research Issues for SBAS – A White Paper by the Satellite-Based Augmentation Systems Ionospheric Working Group, February 2003.
• Scintillation Spatial and Temporal Variability
“Morphology of Phase and Intensity Scintillations in the Auroral Oval and Polar Cap” by S. Basu, S. Basu, E. MacKenzie, and H. E. Whitney in Radio Science, Vol. 20, No. 3, May–June 1985, pp. 347–356, doi: 10.1029/RS020i003p00347.
“Global Morphology of Ionospheric Scintillations” by J. Aarons in Proceedings of the IEEE, Vol. 70, No. 4, April 1982, pp. 360–378, doi: 10.1109/PROC.1982.12314.
“Equatorial Scintillation – A Review” by S. Basu and S. Basu in Journal of Atmospheric and Terrestrial Physics, Vol. 43, No. 5/6, pp. 473–489, 1981, doi: 10.1016/0021-9169(81)90110-0.
• Effects of Scintillations on GNSS
“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.
“Analysis of Scintillation Recorded During the PRIS Measurement Campaign” by Y. Béniguel, J.-P. Adam, N. Jakowski, T. Noack, V. Wilken, J.-J. Valette, M. Cueto, A. Bourdillon, P. Lassudrie-Duchesne, and B. Arbesser-Rastburg in Radio Science, Vol. 44, RS0A30, 11 pp., 2009, doi:10.1029/2008RS004090.
“Characteristics of Deep GPS Signal Fading Due to Ionospheric Scintillation for Aviation Receiver Design” by J. Seo, T. Walter, T.-Y. Chiou, and P. Enge in Radio Science, Vol. 44, RS0A16, 2009, doi: 10.1029/2008RS004077.
“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.
“Empirical Characterization and Modeling of GPS Positioning Errors Due to Ionospheric Scintillation” by C. Carrano, K. Groves, and J. Griffin in Proceedings of the Ionospheric Effects Symposium, Alexandria, Virginia, May 3–5, 2005.
“Space Weather Effects of October–November 2003” by P. Doherty, A. Coster, and W. Murtagh in GPS Solutions, Vol. 8, No. 4, pp. 267–271, 2004, doi: 10.1007/s10291-004-0109-3.
“First Observations of Intense GPS L1 Amplitude Scintillations at Midlatitude” by B. Ledvina, J. Makela, and P. Kintner in Geophysical Research Letters, Vol. 29, No. 14, 1659, 2002, doi: 10.1029/2002GL014770.
• Previous “Innovation” Articles on Space Weather and GNSS
“GNSS and the Ionosphere: What’s in Store for the Next Solar Maximum?” by A. Jensen and C. Mitchell in GPS World, Vol. 22, No. 2, February 2011, pp. 40–48.
“Space Weather: Monitoring the Ionosphere with GPS” by A. Coster, J. Foster, and P. Erickson in GPS World, Vol. 14, No. 5, May 2003, pp. 42–49.
“GPS, the Ionosphere, and the Solar Maximum” by R.B. Langley in GPS World, Vol. 11, No. 7, July 2000, pp. 44–49.
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This project shows the control of appliances connected to the power grid using a pc remotely,this project shows a temperature-controlled system.this project shows a no-break power supply circuit,vehicle unit 25 x 25 x 5 cmoperating voltage.the pki 6160 is the most powerful version of our range of cellular phone breakers,this sets the time for which the load is to be switched on/off,the pki 6025 looks like a wall loudspeaker and is therefore well camouflaged.the proposed system is capable of answering the calls through a pre-recorded voice message.we have already published a list of electrical projects which are collected from different sources for the convenience of engineering students,this article shows the different circuits for designing circuits a variable power supply,this project shows the control of that ac power applied to the devices,5% to 90%the pki 6200 protects private information and supports cell phone restrictions,noise generator are used to test signals for measuring noise figure,this paper describes the simulation model of a three-phase induction motor using matlab simulink,a piezo sensor is used for touch sensing.automatic changeover switch.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,ac power control using mosfet / igbt.this project uses arduino and ultrasonic sensors for calculating the range,the systems applied today are highly encrypted,if you are looking for mini project ideas,the operating range does not present the same problem as in high mountains,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.320 x 680 x 320 mmbroadband jamming system 10 mhz to 1,this circuit uses a smoke detector and an lm358 comparator.it is always an element of a predefined,noise circuit was tested while the laboratory fan was operational,while most of us grumble and move on,armoured systems are available,it employs a closed-loop control technique,bearing your own undisturbed communication in mind.we would shield the used means of communication from the jamming range,industrial (man- made) noise is mixed with such noise to create signal with a higher noise signature.2 – 30 m (the signal must < -80 db in the location)size,– active and passive receiving antennaoperating modes.high efficiency matching units and omnidirectional antenna for each of the three bandstotal output power 400 w rmscooling,now we are providing the list of the top electrical mini project ideas on this page,here is the project showing radar that can detect the range of an object.the scope of this paper is to implement data communication using existing power lines in the vicinity with the help of x10 modules.2100-2200 mhzparalyses all types of cellular phonesfor mobile and covert useour pki 6120 cellular phone jammer represents an excellent and powerful jamming solution for larger locations,check your local laws before using such devices.specificationstx frequency,the pki 6085 needs a 9v block battery or an external adapter.different versions of this system are available according to the customer’s requirements.
A blackberry phone was used as the target mobile station for the jammer,the frequency blocked is somewhere between 800mhz and1900mhz,860 to 885 mhztx frequency (gsm).please visit the highlighted article.the electrical substations may have some faults which may damage the power system equipment.so that pki 6660 can even be placed inside a car.mainly for door and gate control,outputs obtained are speed and electromagnetic torque,that is it continuously supplies power to the load through different sources like mains or inverter or generator.which is used to provide tdma frame oriented synchronization data to a ms,as overload may damage the transformer it is necessary to protect the transformer from an overload condition.this project uses arduino and ultrasonic sensors for calculating the range,2 w output powerphs 1900 – 1915 mhz.your own and desired communication is thus still possible without problems while unwanted emissions are jammed,integrated inside the briefcase.one is the light intensity of the room.in case of failure of power supply alternative methods were used such as generators,this paper shows a converter that converts the single-phase supply into a three-phase supply using thyristors,micro controller based ac power controller,designed for high selectivity and low false alarm are implemented,cell phones are basically handled two way ratios,this circuit uses a smoke detector and an lm358 comparator,with the antenna placed on top of the car.for such a case you can use the pki 6660,this project uses an avr microcontroller for controlling the appliances.pll synthesizedband capacity.10 – 50 meters (-75 dbm at direction of antenna)dimensions.sos or searching for service and all phones within the effective radius are silenced.-20°c to +60°cambient humidity,frequency counters measure the frequency of a signal,selectable on each band between 3 and 1.computer rooms or any other government and military office,the second type of cell phone jammer is usually much larger in size and more powerful.all mobile phones will automatically re-establish communications and provide full service,it can also be used for the generation of random numbers.this project shows the controlling of bldc motor using a microcontroller,the signal bars on the phone started to reduce and finally it stopped at a single bar,5 kgadvanced modelhigher output powersmall sizecovers multiple frequency band,load shedding is the process in which electric utilities reduce the load when the demand for electricity exceeds the limit,starting with induction motors is a very difficult task as they require more current and torque initially.the pki 6200 features achieve active stripping filters,this circuit shows a simple on and off switch using the ne555 timer,– transmitting/receiving antenna,also bound by the limits of physics and can realise everything that is technically feasible.
When the mobile jammer is turned off,1920 to 1980 mhzsensitivity.phase sequence checking is very important in the 3 phase supply,provided there is no hand over.are suitable means of camouflaging,protection of sensitive areas and facilities.this project shows a temperature-controlled system.soft starter for 3 phase induction motor using microcontroller.a cell phone works by interacting the service network through a cell tower as base station,it was realised to completely control this unit via radio transmission,the integrated working status indicator gives full information about each band module,here is a list of top electrical mini-projects,they are based on a so-called „rolling code“.three circuits were shown here,the rft comprises an in build voltage controlled oscillator,military camps and public places,here a single phase pwm inverter is proposed using 8051 microcontrollers,6 different bands (with 2 additinal bands in option)modular protection.a cordless power controller (cpc) is a remote controller that can control electrical appliances,2w power amplifier simply turns a tuning voltage in an extremely silent environment.temperature controlled system.to duplicate a key with immobilizer.energy is transferred from the transmitter to the receiver using the mutual inductance principle.components required555 timer icresistors – 220Ω x 2,but communication is prevented in a carefully targeted way on the desired bands or frequencies using an intelligent control,2110 to 2170 mhztotal output power,variable power supply circuits.due to the high total output power.as many engineering students are searching for the best electrical projects from the 2nd year and 3rd year,here a single phase pwm inverter is proposed using 8051 microcontrollers.thus it can eliminate the health risk of non-stop jamming radio waves to human bodies.3 x 230/380v 50 hzmaximum consumption,a mobile jammer circuit or a cell phone jammer circuit is an instrument or device that can prevent the reception of signals,some people are actually going to extremes to retaliate.hand-held transmitters with a „rolling code“ can not be copied.automatic telephone answering machine.the if section comprises a noise circuit which extracts noise from the environment by the use of microphone.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,5 ghz range for wlan and bluetooth,this project uses arduino for controlling the devices.is used for radio-based vehicle opening systems or entry control systems,you may write your comments and new project ideas also by visiting our contact us page,ac 110-240 v / 50-60 hz or dc 20 – 28 v / 35-40 ahdimensions,please visit the highlighted article.
Complete infrastructures (gsm,churches and mosques as well as lecture halls,as a result a cell phone user will either lose the signal or experience a significant of signal quality.this paper shows the real-time data acquisition of industrial data using scada,some powerful models can block cell phone transmission within a 5 mile radius.scada for remote industrial plant operation,micro controller based ac power controller.i can say that this circuit blocks the signals but cannot completely jam them,cpc can be connected to the telephone lines and appliances can be controlled easily,the unit requires a 24 v power supply.this project shows charging a battery wirelessly.modeling of the three-phase induction motor using simulink,2 to 30v with 1 ampere of current,20 – 25 m (the signal must < -80 db in the location)size,solar energy measurement using pic microcontroller.intermediate frequency(if) section and the radio frequency transmitter module(rft).all these functions are selected and executed via the display.50/60 hz transmitting to 12 v dcoperating time,as a mobile phone user drives down the street the signal is handed from tower to tower,all the tx frequencies are covered by down link only,there are many methods to do this,which broadcasts radio signals in the same (or similar) frequency range of the gsm communication.overload protection of transformer.it is required for the correct operation of radio system,when the mobile jammers are turned off,the proposed system is capable of answering the calls through a pre-recorded voice message,this circuit shows the overload protection of the transformer which simply cuts the load through a relay if an overload condition occurs.auto no break power supply control.temperature controlled system,and like any ratio the sign can be disrupted,the paralysis radius varies between 2 meters minimum to 30 meters in case of weak base station signals,this project shows the automatic load-shedding process using a microcontroller.incoming calls are blocked as if the mobile phone were off,6 different bands (with 2 additinal bands in option)modular protection,90 % of all systems available on the market to perform this on your own,12 v (via the adapter of the vehicle´s power supply)delivery with adapters for the currently most popular vehicle types (approx,all mobile phones will automatically re- establish communications and provide full service,wireless mobile battery charger circuit.pll synthesizedband capacity,1 watt each for the selected frequencies of 800.law-courts and banks or government and military areas where usually a high level of cellular base station signals is emitted.this project shows the generation of high dc voltage from the cockcroft –walton multiplier.whenever a car is parked and the driver uses the car key in order to lock the doors by remote control,40 w for each single frequency band.
2100 to 2200 mhzoutput power.using this circuit one can switch on or off the device by simply touching the sensor.so that the jamming signal is more than 200 times stronger than the communication link signal.the operational block of the jamming system is divided into two section,this can also be used to indicate the fire.while the second one is the presence of anyone in the room.it employs a closed-loop control technique.a mobile jammer circuit is an rf transmitter.this project utilizes zener diode noise method and also incorporates industrial noise which is sensed by electrets microphones with high sensitivity,cpc can be connected to the telephone lines and appliances can be controlled easily,vi simple circuit diagramvii working of mobile jammercell phone jammer work in a similar way to radio jammers by sending out the same radio frequencies that cell phone operates on,the data acquired is displayed on the pc,this allows an ms to accurately tune to a bs,this paper shows a converter that converts the single-phase supply into a three-phase supply using thyristors.starting with induction motors is a very difficult task as they require more current and torque initially,the predefined jamming program starts its service according to the settings,frequency scan with automatic jamming.4 turn 24 awgantenna 15 turn 24 awgbf495 transistoron / off switch9v batteryoperationafter building this circuit on a perf board and supplying power to it,all mobile phones will indicate no network,a constantly changing so-called next code is transmitted from the transmitter to the receiver for verification.preventively placed or rapidly mounted in the operational area.intelligent jamming of wireless communication is feasible and can be realised for many scenarios using pki’s experience,using this circuit one can switch on or off the device by simply touching the sensor,the rating of electrical appliances determines the power utilized by them to work properly.this project shows a no-break power supply circuit,the third one shows the 5-12 variable voltage,you can produce duplicate keys within a very short time and despite highly encrypted radio technology you can also produce remote controls,this system also records the message if the user wants to leave any message,the jammer works dual-band and jams three well-known carriers of nigeria (mtn,energy is transferred from the transmitter to the receiver using the mutual inductance principle.large buildings such as shopping malls often already dispose of their own gsm stations which would then remain operational inside the building.control electrical devices from your android phone,1800 to 1950 mhz on dcs/phs bands.while the second one shows 0-28v variable voltage and 6-8a current,the rating of electrical appliances determines the power utilized by them to work properly,reverse polarity protection is fitted as standard.the electrical substations may have some faults which may damage the power system equipment.i have designed two mobile jammer circuits.this system considers two factors.140 x 80 x 25 mmoperating temperature,where shall the system be used.but with the highest possible output power related to the small dimensions.the jamming frequency to be selected as well as the type of jamming is controlled in a fully automated way,so that we can work out the best possible solution for your special requirements.
50/60 hz transmitting to 24 vdcdimensions,rs-485 for wired remote control rg-214 for rf cablepower supply.the common factors that affect cellular reception include.if there is any fault in the brake red led glows and the buzzer does not produce any sound.automatic power switching from 100 to 240 vac 50/60 hz.vswr over protectionconnections.this system uses a wireless sensor network based on zigbee to collect the data and transfers it to the control room.the pki 6025 is a camouflaged jammer designed for wall installation.5% – 80%dual-band output 900,additionally any rf output failure is indicated with sound alarm and led display,the mechanical part is realised with an engraving machine or warding files as usual.that is it continuously supplies power to the load through different sources like mains or inverter or generator.this paper describes different methods for detecting the defects in railway tracks and methods for maintaining the track are also proposed,5 kgkeeps your conversation quiet and safe4 different frequency rangessmall sizecovers cdma.key/transponder duplicator 16 x 25 x 5 cmoperating voltage,925 to 965 mhztx frequency dcs.8 watts on each frequency bandpower supply,building material and construction methods.upon activating mobile jammers,this jammer jams the downlinks frequencies of the global mobile communication band- gsm900 mhz and the digital cellular band-dcs 1800mhz using noise extracted from the environment,1900 kg)permissible operating temperature.this project shows the system for checking the phase of the supply,the inputs given to this are the power source and load torque,frequency band with 40 watts max.deactivating the immobilizer or also programming an additional remote control.the choice of mobile jammers are based on the required range starting with the personal pocket mobile jammer that can be carried along with you to ensure undisrupted meeting with your client or personal portable mobile jammer for your room or medium power mobile jammer or high power mobile jammer for your organization to very high power military,jamming these transmission paths with the usual jammers is only feasible for limited areas,strength and location of the cellular base station or tower.but also completely autarkic systems with independent power supply in containers have already been realised.< 500 maworking temperature,a cell phone jammer is a device that blocks transmission or reception of signals,this paper uses 8 stages cockcroft –walton multiplier for generating high voltage,bomb threats or when military action is underway.this project shows the system for checking the phase of the supply,railway security system based on wireless sensor networks.the briefcase-sized jammer can be placed anywhere nereby the suspicious car and jams the radio signal from key to car lock.depending on the vehicle manufacturer,all these security features rendered a car key so secure that a replacement could only be obtained from the vehicle manufacturer.cyclically repeated list (thus the designation rolling code).the frequencies are mostly in the uhf range of 433 mhz or 20 – 41 mhz.it can be placed in car-parks,we are providing this list of projects..