Spatial Decorrelation Analysis of Ionospheric Delay Due to the Medium-Scale Traveling Ionospheric Disturbances using Radio-over-Fiber Devices and a Single Clock Receiver for Extended Baselines

Takayuki Yoshihara and Susumu Saito

Peer Reviewed

Abstract:	This study focuses on spatial decorrelation of ionospheric delay observed with a baseline length of several kilometers. In particular, we aim to observe spatial and temporal variations of the mid-latitude nighttime medium-scale traveling ionospheric disturbances (MSTIDs) with a small horizontal scale of several kilometers. To extract small perturbation of ionospheric delay difference with a short baseline, we use a multi-RF-port GNSS receiver together with Radio-over-Fiber (RoF) devices. Using them, we built an observational system to use a common clock for signal processing of RF inputs from two GNSS antennas with a separation of 2.3 km. Through geometrical correction process using GNSS satellite orbit information and a set of the pre-analyzed GNSS antenna positions, common-satellite single differences in carrier phase measurements based on single frequency of L1 signals represent atmospheric delay differences between the two GNSS antennas without necessity to consider or estimate a component of receiver clock errors. As the first step of analysis, we examined the single differences of SBAS (Satellite-Based Augmentation System) ranging signals. Because SBAS is geo-stationary satellite, a time series of its ranging signal contains temporal variations of atmospheric delay along the “stationary” path. We carefully extracted and confirmed ionospheric delay differences with distinction from tropospheric delay. As results, the variations with large spatial gradients up to ±54 mm/km in slant direction were found in the observational data nighttime on 26th May, 2016. The results are larger than the typical value for overall structure of the mid-latitude nighttime MSTIDs. There are two possibilities to explain the results. The first is the observational results might be resulted from disturbances in the E region. Another possibility is that the results also represent structure of disturbances including in the F region. Although it is necessary to increase a number of analysis for the similar events, the result suggests that there are smaller scale structures in the mid-latitude nighttime MSTIDs than the scale of the overall structure. It is also necessary to reconsider its impact on navigation systems and positioning applications.
Published in:	Proceedings of the 31st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2018) September 24 - 28, 2018 Hyatt Regency Miami Miami, Florida
Pages:	4094 - 4101
Cite this article:	Yoshihara, Takayuki, Saito, Susumu, "Spatial Decorrelation Analysis of Ionospheric Delay Due to the Medium-Scale Traveling Ionospheric Disturbances using Radio-over-Fiber Devices and a Single Clock Receiver for Extended Baselines," Proceedings of the 31st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2018), Miami, Florida, September 2018, pp. 4094-4101. https://doi.org/10.33012/2018.15919
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