Browsing by Subject "TEC"
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Item Open Access Interpolation of ionospheric modalities using kriging, co-kriging and spatio-temporal kriging(Bilkent University, 2018-06) Khaf, SadiaLong distance communication and navigation systems operating in the HF band use interacting signals as they travel through the ionosphere. It is important to accurately model ionospheric behavior to increase the performance of these systems. Delays occurring in the signals depend on the refrectivity which is a function of frequency of the signals, and the electron density on the signal path at the time of propagation. Depending on the change in the solar activities, the electron distribution in the ionosphere changes spatially and temporally. The change in ionosphere can be tracked by various parameters and the space-time distribution of these parameters. Total Electron Content (TEC), the total number of electrons in a cylinder with one meter square cross-sectional area over a ray path is used as an important descriptor for the ionosphere. It is possible to generate TEC maps with high spatial resolution using the information obtained by processing the GPS satellite signals by constantly operating reference stations (CORS) GPS receivers. In particular, there are two other parameters that are used in HF communication and direction nding applications: foF2, which is the highest plasma frequency of foF2 layer, and hmF2, which is the height of maximum ionization. Sensitive foF2 and hmF2 measurements can be made by ionosonde systems. However, these systems are highly sparser than TEC measurements. For this reason, the resolution of the foF2 and hmF2 maps is less than the TEC maps. In this study, we propose a space-time mapping technique based on Co-Kriging which is used in conjunction with TEC data, that is correlated to these parameters, to increase the resolutions of foF2 and hmF2 maps. The performance of the proposed technique is compared with the alternatives and the increase in performance achieved is described statistically.Item Open Access Space weather activities of IONOLAB group using TNPGN GPS Network(IEEE, 2011) Aktug, B.; Lenk O.; Kurt, M.; Parmaksiz, E.; Ozdemir, S.; Arikan F.; Sezen, U.; Toker, C.; Arıkan, OrhanCharacterization and constant monitoring of variability of the ionosphere is of utmost importance for the performance improvement of HF communication, Satellite communication, navigation and guidance systems, Low Earth Orbit (LEO) satellite systems, Space Craft exit and entry into the atmosphere and space weather. Turkish National Permanent GPS Network (TNPGN) is the Reference Station Network of 146 continuously-operating GNSS stations of which are distributed uniformly across Turkey and North Cyprus Turkish Republic since May 2009. IONOLAB group is currently investigating new techniques for space-time interpolation, and automatic mapping of TEC through a TUBITAK research grant. It is utmost importance to develop regional stochastic models for correction of ionospheric delay in geodetic systems and also form a scientific basis for communication link characterization. This study is a brief summary of the efforts of IONOLAB group in monitoring of space weather, and correction of geodetic positioning errors due to ionosphere using TNPGN. © 2011 IEEE.