Impact of space weather events on satellite-based navigation
01 Dec 2013-Space Weather-the International Journal of Research and Applications (John Wiley & Sons, Ltd)-Vol. 11, Iss: 12, pp 680-686
TL;DR: In this article, the received phase of the L1(1575.42 MHz) signal from two stations, namely Calcutta situated near the northern crest of the Equatorial Ionization Anomaly and Siliguri, at a subionospheric latitude separation of 4° along the same meridian.
Abstract: Detrimental effects of the equatorial ionospheric irregularities on satellite-based communication and navigation systems have been studied over the past few decades as space weather events have the potential to seriously disturb the technological infrastructure of modern society. The present paper tries to understand operational compliance of Global Positioning System (GPS) receivers to International Civil Aviation Organization (ICAO) standards under scintillation conditions by recording the received phase of the L1(1575.42 MHz) signal from two stations, namely Calcutta situated near the northern crest of the Equatorial Ionization Anomaly and Siliguri, situated beyond the northern crest, at a subionospheric latitude separation of 4° along the same meridian. A causative approach is adopted whereby GPS phase scintillations have been monitored and receiver performance prior to loss of lock and cycle slips have been analyzed during August–October 2011 at Calcutta and September 2011 at Siliguri. The received phase at GPS-L1 frequency has often been found to fluctuate at kilohertz, often megahertz rates, thereby causing carrier-tracking loop malfunctions. It should be borne in mind that normal GPS receivers' carrier-tracking loops have a typical dynamic range of 14–18 Hz. Cycle slips have been observed with durations far exceeding ICAO specified levels for high dynamic platforms like aircrafts. Differences in cycle slips between Calcutta and Siliguri indicate possible evolution of irregularity structures even across small subionospheric swath. Significant improvement in present understanding of GPS phase scintillations should be developed and implemented in receiver designs prior to application of Satellite Based Augmentation System services for civil aviation, particularly in the geophysically sensitive equatorial region.
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TL;DR: The International GNSS Service (IGS) has recently accepted for official release a new ionospheric product to characterize ionosphere irregularity and intensity as derived from multi-site ground-based GPS observations as mentioned in this paper.
Abstract: The International GNSS Service (IGS) has recently accepted for official release a new ionospheric product to characterize ionospheric irregularity and intensity as derived from multi-site ground-based GPS observations. This product was developed and implemented in the Space Radio-Diagnostic Research Center (SRRC), University of Warmia and Mazury. The SRRC has implemented this approach using in-house software for multi-step processing and interpretation of carrier phase delays in dual-frequency GPS signals and provides the new product to the IGS database. We used measurements with 30-s sampling rate from about 700 GPS stations located at high and middle latitudes of the Northern Hemisphere. The product represents changes in the GPS-based Rate of TEC Index (ROTI) and has a polar projection within a range of 50°–90°N in geomagnetic latitude and 00–24 magnetic local time. The new service allows regular monitoring of ionospheric irregularities over the Northern Hemisphere. We demonstrate results of visualization and analysis of the IGS ROTI Maps product for representative periods with geomagnetically quiet conditions and severe geomagnetic storms in 2014–2015 in order to demonstrate the performance and ability of this product to depict the development of ionospheric irregularities in the area of interest. During space weather events, the ionospheric irregularities oval, as deduced from the ROTI Maps, expands significantly in size toward midlatitudes with simultaneous increase in irregularities intensity, which can lead to degradation of the GPS precise positioning performance at lower latitudes.
68 citations
TL;DR: In this paper, the authors examined global features of the large-scale plasma depletion by using a combination of ground-based and space-borne measurements, including GPS/GNSS, GPS Radio Occultation (RO), Swarm upward looking GPS data, and in situ plasma density observations provided by Swarm, Communications/Navigation Outage Forecasting System (C/NOFS), and Defense Meteorological Satellite Program (DMSP) missions.
Abstract: June solstice is considered as a period with the lowest probability to observe typical equatorial plasma bubbles (EPBs) in the postsunset period. The severe geomagnetic storm on 22–23 June 2015 has drastically changed the situation. Penetrating electric fields associated with a long‐lasting southward IMF support favorable conditions for postsunset EPBs generation in the dusk equatorial ionosphere for several hours. As a result, the storm‐induced EPBs were progressively developed over a great longitudinal range following the sunset terminator. The affected area has a large longitudinal range of ~100° in the American sector and a rather localized zone of ~20° in longitude in the African sector. Plasma depletions of equatorial origin were registered at midlatitudes (30°–40° magnetic latitude) of both hemispheres in the African and American longitudinal sectors. We examine global features of the large‐scale plasma depletion by using a combination of ground‐based and space‐borne measurements—ground‐based Global Positioning System/Global Navigation Satellite System (GPS/GNSS) networks, Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) GPS Radio Occultation (RO), Swarm upward looking GPS data, and in situ plasma density observations provided by Swarm, Communications/Navigation Outage Forecasting System (C/NOFS), and Defense Meteorological Satellite Program (DMSP) missions. Joint analysis of the satellite observations revealed that these storm‐induced EPBs structures had extended over 500 km in altitude, at least from ~350 to ~850 km. These irregularities caused strong amplitude and phase scintillations of GPS/GNSS signals for ground‐based and space‐borne (COSMIC RO) measurements and seriously affected performance of navigation‐based services.
41 citations
TL;DR: The largest geomagnetic storm in solar cycle 24 occurred during March 17-18, 2015 where the main phase of the storm reached the negative minimum at 22:00 UT as discussed by the authors.
Abstract: The largest geomagnetic storm in solar cycle 24 occurred during March 17-18, 2015 where the main phase of the storm commenced from 07:00 UT of March 17, 2015 and reached the Dst negative minimum at 22:00 UT. The present paper reports observations of TEC, amplitude and phase scintillations from different GPS stations of India during the storm of March 17 and highlights its effects on GPS. It also presents the global ESF occurrence during the storm using total ion density drift measurements from C/NOFS satellite. TEC enhancements were noted from stations along 77oE meridian around 10:00 UT on March 17 compared to March 16 and 18 indicating positive storm effects arising out of equatorward neutral wind in the local morning-noon sector of the main phase. Intense scintillation observations from Calcutta were most extensive during 15:00-16:00 UT, March 17 and the receiver recorded a longitude deviation of 5.2 m during this time. Cycle slips of the order of 8 s could be observed during periods of intense phase scintillations on the same night. Intense scintillation observation from Palampur is an exceptional phenomenon attributed to the dramatic enhancement of the electric field due to PPEF leading to a very high upward ion velocity over the magnetic equator as recorded by C/NOFS. The total ion density measured globally by C/NOFS reveals two distinct longitude regions of ESF occurrence during the storm: i) East Pacific sector and ii) Indian longitude during the storm. The time and longitude of ESF occurrence could be predicted using the time of southward turning of IMF Bz.
33 citations
TL;DR: In this paper, the authors provided the proportion of time during scintillation patches that decorrelations are found across GPS L1, L2 and L5 frequencies associated with high S4, corresponding high values of scattering coefficients and large receiver position deviations thereby seriously compromising the performance of satellite based navigation system.
Abstract: Multi-frequency GPS transmissions have provided the opportunity for testing the applicability of the principle of frequency diversity for scintillation mitigation. Published results addressing this issue with quantified estimates are not available in literature, at least from the anomaly crest location of the Indian longitude sector. Multi-frequency scattering within the same L-band are often the attributed cause behind simultaneous decorrelated signal fluctuations. The present paper aims to provide proportion of time during scintillation patches that decorrelations are found across GPS L1, L2 and L5 frequencies associated with high S4, corresponding high values of scattering coefficients and large receiver position deviations thereby seriously compromising the performance of satellite based navigation system. Results from the anomaly crest station at Calcutta indicate maximum 40% of scintillation time during February-April 2014 and 33% during August-October 2014 that the signals are decorrelated. It is important to note that it is only during these time intervals that the principle of frequency diversity could be applied for scintillation mitigation.
18 citations
Cites background from "Impact of space weather events on s..."
...…transionospheric satellite signals often resulting in complete outage of the signal leading to severe degradation of services of satellite-based communication and navigation systems which may pose life-critical conditions, particularly for high dynamic platforms like aircrafts (Roy & Paul, 2013)....
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TL;DR: In this article, a dynamical response of the high-latitude topside ionosphere to the intense geomagnetic storm was analyzed using up-looking GPS measurements on board Swarm and Meteorological Operational satellite (MetOp) missions, flying at altitudes of ~500 km and ~835 km, respectively.
Abstract: Many of currently operated low Earth orbit satellites, in particular Earth observing meteorological missions, are equipped with dual-frequency Global Positioning System (GPS) receivers with a zenith-looking antenna for tasks of precise orbit determination and timing. The already existed databases with accumulated raw GPSmeasurements, as a by-product of satellite missions, can arouse specific interest for ionospheric and space weather community too. We demonstrate potential possibilities and advantages of involving underutilized spaceborne GPS measurements for Space Weather activity monitoring by specification of storm-induced ionospheric plasma density irregularities at different altitudinal domain of the topside ionosphere. We have analyzed a dynamical response of the high-latitude topside ionosphere to the intense geomagnetic storm of 19–21 December 2015 using up-looking GPS measurements on board Swarm and Meteorological Operational satellite (MetOp) missions, flying at altitudes of ~500 km and ~835 km, respectively. For the first time, GPS observations on board the meteorological mission MetOp were used to reveal an occurrence of plasma irregularities at altitudes above 835 km. Our results demonstrate that during strong geomagnetic storms the intense plasma density irregularities can occur in the topside ionosphere near ~500 km altitude and can be still persisted above 835 km. Joint analysis of the Super Dual Auroral Radar Network global convection patterns, ground-based GPS total electron content (TEC) observations, and MetOp-derived topside TEC observations confirmed that plasma irregularities above ~835 km coincided with the plasmaspheric/magnetospheric part of the storm-enhanced density and the polar tongue of ionization structures, which is the first direct observation of the storm-enhanced density/tongue of ionization structure in the plasmaspheric TEC.
15 citations
Cites background from "Impact of space weather events on s..."
...On the one hand, it can lead to a serious degradation or even outage of critical systems performance, in particular GNSS-based ones (e.g., Basu et al., 2008; Doherty et al., 2004; Roy et al., 2013)....
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References
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TL;DR: In this article, a characterization of the behavior of phase tracking loops in the presence of severe equatorial ionospheric scintillation is given, and a differentially detected bit error model is proposed to predict cycle slipping rates.
Abstract: A characterization is given for the behavior of Global Positioning System phase tracking loops in the presence of severe equatorial ionospheric scintillation. The purpose of this work is to develop a simple, general, and realistic scintillation effects model that can be used to improve the scintillation performance of phase tracking loops. The new characterization of scintillation effects proposed herein employs a differentially detected bit error model to predict cycle slipping rates that approximately agree with data-driven simulation tests.
153 citations
"Impact of space weather events on s..." refers background in this paper
...There are efforts globally to understand the design of receiver carrier phase tracking loops necessary to maintain lock even in the presence of severe equatorial scintillations [Humphreys et al., 2010]....
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TL;DR: In this paper, the effect of scintillation fades on the operation of GPS receivers is investigated, with special attention given to the effect on the SCINTillation timescales on the CDMA protocol used by GPS.
Abstract: The effect of equatorial ionospheric scintillations on the operation of GPS receivers is investigated, with special attention given to the effect of scintillation timescales on the code division multiple access (CDMA) protocol used by GPS. We begin by examining the timescales of scintillation fades modeled as a horizontally drifting pattern whose timescales are determined by the Fresnel length and the drift speed. The model is tested by comparing the speed, determined by dividing the Fresnel length by the autocorrelation time (width), with the speed estimated using spaced receivers, and the two independent estimates of speed are shown to possess a linear relationship. Next we show that the scintillation pattern drift speed is given by the difference of the ionospheric drift and the speed of the GPS signal F region puncture point. When the ionosphere and GPS signal puncture point speeds match, the fade timescales lengthen. Additionally, if the fade depth is adequate, during periods of longer fade times the loss of receiver lock on GPS signals is more likely, as shown in several examples; that is, both larger fade depths and longer fade timescales are required to produce loss of tracking. We conclude by demonstrating that speed matching or resonance between the ionosphere and receiver is most likely when the receiver is moving from west to east at speeds of 40–100 m/s (144–360 km/h). This is in the range of typical aircraft speeds.
131 citations
"Impact of space weather events on s..." refers background in this paper
...SPACE WEATHER, VOL. 11, 680–686, doi:10.1002/2013SW001001, 2013 et al., 1997; Kintner et al., 2001, 2004; DasGupta et al., 2004; de Paula et al., 2010]....
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...…motion between drifting ionospheric irregularities and GPS satellite vehicles on the receiver tracking loop performance, particularly under conditions of resonance, may lead to higher probability of loss of lock due to the longer duration of the amplitude fades [Kintner et al., 2001, 2004]....
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DOI•
16 Sep 2005
TL;DR: In this paper, the performance of several GPS carrier tracking loops is evaluated using wideband GPS data recorded during strong ionospheric scintillations, and a proposed variable-bandwidth loop based on a Kalman filter is proposed.
Abstract: The performance of several GPS carrier tracking loops is evaluated using wideband GPS data recorded during strong ionospheric scintillations. The aim of this study is to determine the loop structures and parameters that enable good phase tracking during the power fades and phase dynamics induced by scintillations. Constant-bandwidth and variable-bandwidth loops are studied using theoretical models, simulation, and tests with actual GPS signals. Constant-bandwidth loops with loop bandwidths near 15 Hz are shown to lose phase lock during scintillations. Use of the decision-directed discriminator reduces the carrier lock threshold by »1 dB relative to the arctangent and conventional Costas discriminators. A proposed variablebandwidth loop based on a Kalman filter reduces the carrier lock threshold by more than 7 dB compared to a 15-Hz constant-bandwidth loop. The Kalman filter-based strategy employs a soft-decision discriminator, explicitly models the eects of receiver clock noise, and optimally adapts the loop bandwidth to the carrier-to-noise ratio. In extensive simulation and in tests using actual wideband GPS data, the Kalman filter PLL demonstrates improved cycle slip immunity relative to constant bandwidth PLLs.
102 citations
"Impact of space weather events on s..." refers background in this paper
...Strong phase scintillations have the potential to stress phase lock loops (PLL) in GPS/GNSS receivers resulting in loss of phase lock and frequent cycle slips, thereby impeding carrier phase measurements [Humphreys et al., 2005]....
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TL;DR: In this article, GPS L1 C/A signal scintillation data were collected at the equatorial anomaly over a period of three months using five receivers spaced on magnetic east-west and north-south axes.
Abstract: [1] GPS L1 C/A signal scintillation data were collected at the equatorial anomaly over a period of three months using five receivers spaced on magnetic east-west and north-south axes to examine the speed, orientation, shape, width, and duration of GPS scintillation fade patterns. The nighttime speeds were primarily eastward in the range of 100–200 m/s with a significant spread to both larger values and negative (westward) values as expected, given the known behavior of ionospheric drifts and GPS signal path movement. The characteristic velocity was found to be small so that the true velocity was equal to the apparent velocity to a very good approximation. The orientation of the scintillation fade patterns was organized by a simple projection model of the magnetic field along the GPS signal path onto the horizontal plane when the signal paths were aligned no closer than 60° from the magnetic field. The shape of the scintillation fade pattern was greatly elongated in the magnetic north-south direction, and no change could be detected over a distance of 1 km. The east-west widths of the scintillation fade patterns were variable, but after normalizing to the elevation angle, accounting for the fade orientation, and eliminating signal paths within 60° of the magnetic field, an organized scale length of about 450 m was determined. The duration of the scintillation fade patterns was examined using the optimal cross-correlation amplitude as a measure of change. For a 5 s duration, 49% of the optimal cross-correlation amplitudes exceed a value of 0.8.
98 citations
"Impact of space weather events on s..." refers background in this paper
...SPACE WEATHER, VOL. 11, 680–686, doi:10.1002/2013SW001001, 2013 et al., 1997; Kintner et al., 2001, 2004; DasGupta et al., 2004; de Paula et al., 2010]....
[...]
...…motion between drifting ionospheric irregularities and GPS satellite vehicles on the receiver tracking loop performance, particularly under conditions of resonance, may lead to higher probability of loss of lock due to the longer duration of the amplitude fades [Kintner et al., 2001, 2004]....
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