Abstract

Over the last 15 years, the satellite constellation of the global positioning system (GPS) has been modernized for more precise applications, with the introduction of the L2C and L5 signals. However, among other effects, they are susceptible to severe ionospheric effects, particularly in the equatorial and low-latitude regions. Equatorial plasma bubbles, resulting from the combination of the ionospheric electrodynamics with plasma instability mechanisms and thermospheric coupling, may generate irregularity structures with scale sizes ranging from hundreds of kilometers to a few meters (or less). Ionospheric irregularities may cause deep amplitude fades and phase shifts to transionospheric signals. That is, they are responsible for amplitude and phase scintillation, which degrade receiver operations and may cause failures and unavailability to positioning and navigation services under extreme conditions. The objective of the present work is to analyze ionospheric scintillation effects on the L2C and L5 GPS signals, to compare their vulnerabilities with those of the L1 signal. The data used in this analysis were collected between November 2014 and March 2015, during the maximum solar activity of cycle 24 (a period of great scintillation incidence), by scintillation monitors deployed at four different sites in the Brazilian territory: Fortaleza, Presidente Prudente, São José dos Campos, and Porto Alegre. Intensity fades will be analyzed, considering different thresholds, to reveal their empirical probability distributions of scintillation occurrence, average fading occurrences and durations. The results will show that greater probabilities of strong scintillation occurrences are present in the modernized signals, reaching up to five times more events in the L5 signal in comparison with those in the legacy L1 signal. It will be shown that the L5 average fade duration is distinctly longer than the corresponding ones for the other frequencies, considering the same site, threshold, and L1 amplitude scintillation level. The results will also show that the average fade duration decreases according to the average ratio 0.6 s/3 dB within the threshold range from − 6 to − 15 dB, considering the same amplitude scintillation level and location.

中文翻译：

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研究电离层闪烁对多频GPS信号的影响

摘要

在过去的15年中，通过引入L2C和L5信号，对全球定位系统（GPS）的卫星星座进行了现代化改造，以实现更精确的应用。但是，除其他影响外，它们还容易受到严重的电离层影响，特别是在赤道和低纬度地区。由电离层电动力学与等离子不稳定性机制和热层耦合引起的赤道等离子气泡可能会产生不规则结构，其尺度范围从数百公里到几米（或更小）。电离层的不规则性可能会导致幅度衰减变深并且相移到跨电离层信号。也就是说，它们负责幅度和相位闪烁，这会降低接收器的运行性能，并可能导致极端条件下的定位和导航服务出现故障和无法使用。本工作的目的是分析电离层闪烁对L2C和L5 GPS信号的影响，以比较它们与L1信号的脆弱性。此分析中使用的数据是在2014年11月至2015年3月的第24个周期的最大太阳活动期间（发生强烈闪烁事件）收集的，该闪烁监视器由部署在巴西境内四个不同地点的闪烁监测仪组成：圣若泽·多斯·坎波斯和阿雷格里港。将考虑不同的阈值对强度衰减进行分析，以揭示其闪烁发生，平均衰落发生和持续时间的经验概率分布。结果将表明，在现代化信号中存在发生强烈闪烁的可能性更高，与传统L1信号相比，L5信号的事件最多发生五倍。可以看出，考虑到相同的位置，阈值和L1幅度闪烁水平，L5平均衰落持续时间明显长于其他频率的相应衰落持续时间。结果还将显示，在相同幅度闪烁水平和位置的情况下，平均衰减持续时间在-6至-15 dB的阈值范围内根据平均比0.6 s / 3 dB减小。与传统L1信号中的事件相比，L5信号中的事件数量最多增加了五倍。可以看出，考虑到相同的位置，阈值和L1幅度闪烁水平，L5平均衰落持续时间明显长于其他频率的相应衰落持续时间。结果还将显示，在相同幅度闪烁水平和位置的情况下，平均衰减持续时间在-6至-15 dB的阈值范围内根据平均比0.6 s / 3 dB减小。与传统L1信号中的事件相比，L5信号中的事件数量最多增加了五倍。可以看出，考虑到相同的位置，阈值和L1幅度闪烁水平，L5平均衰落持续时间明显长于其他频率的相应衰落持续时间。结果还将显示，在相同幅度闪烁水平和位置的情况下，平均衰减持续时间在-6至-15 dB的阈值范围内根据平均比0.6 s / 3 dB减小。