A Comparison of GNSS-based Ionospheric Scintillation Observations in North and South Hong Kong

Z. Liu, R. Xu, J. Morton, J. Xu, W. Pelgrum, S. Taylor, W. Chen, and X. Ding

Abstract:	Ionosphere scintillation is caused by irregularities of electron density when radio wave passes through the ionosphere. It leads to random fluctuations in the amplitude and phase of satellite signals, degrading the performance of the satellites based navigation system such as the Global Positioning System (GPS) and other global navigation satellite systems (GNSS). Ionosphere scintillation results in increased navigation errors and may lead to loss-of-lock of satellite signals during strong events. Scintillations are more often observed in equatorial and high latitude areas. Hong Kong, located in a low latitude region (geographic 22.3°N, 114.2°E), frequently experiences serious ionospheric scintillations. This poses a threat to the reliability and accuracy of Hong Kong GNSS applications. In this study, two GNSS-based ionospheric scintillation receivers were used to monitor scintillations in south and north Hong Kong. The south station (HKHT) is equipped with a Septentrio PolaRxS Pro GNSS receiver while the north station (HKST) is equipped with a custom-modified GNSS receiver with a NovAtel OEMV board. Both stations were established in 2012 and are separated by 24 km. The HKHT station provides high-frequency scintillation data, including 50 Hz carrier phase measurements and 100 Hz outputs of correlators (in-phases and quadra-phases). The HKST station outputs 20 Hz carrier phase measurements and carrier-to-noise density (C/N0). In this paper, we first computed the scintillation indices S4 and ??, and then analyzed their temporal and spatial distributions over the two stations. The characteristics of amplitudes and phase scintillations at the south and north Hong Kong stations were compared and analyzed. Our observation results during 16-31 August 2012 showed that both amplitudes and phase scintillations were most observed during 20:00-3:00 LT (LT=UT+8 hours) in Hong Kong. For the stronger scintillations (S4?0.4 or ???0.4 rad), most occurred during 20:00-23:00 LT. In terms of spatial distribution, amplitude scintillations (0.2?S4 0.4) and phase scintillations (0.2??? 0.4 rad) could be observed almost over the entire sky at both stations. A majority of stronger scintillation (S4?0.4 or ???0.4) occurred on the signals from the satellites in the south region with azimuth from 120 to 240 degrees. Moreover, there were more and stronger amplitude scintillations than phase scintillations. There are also significant differences between the observations of scintillations at the two stations. We believe that these differences are due to the quality and performance of the two GNSS receivers.
Published in:	Proceedings of the ION 2013 Pacific PNT Meeting April 23 - 25, 2013 Marriott Waikiki Beach Resort & Spa Honolulu, Hawaii
Pages:	694 - 705
Cite this article:	Liu, Z., Xu, R., Morton, J., Xu, J., Pelgrum, W., Taylor, S., Chen, W., Ding, X., "A Comparison of GNSS-based Ionospheric Scintillation Observations in North and South Hong Kong," Proceedings of the ION 2013 Pacific PNT Meeting, Honolulu, Hawaii, April 2013, pp. 694-705.
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