Study of Ionospheric Effects on Space Communication and Navigation

Radiowave scintillation caused by ionospheric density irregularities will degrade the space communication/navigation quality. The goal of the proposed project is to study the irregularity characteristics and global occurrence distributions (solar maximum vs. solar minimum) so as to assess the impacts on communication, navigation and positioning system.The first part of the project is to study the density irregularity events observed by the space-borne payload Advanced Ionospheric Probe (AIP) on FORMOSAT-5 and the scintillation events observed by the ground AFRL-NCU SCINDA Station at southern Taiwan. The scintillation data will routinely give us the background ionospheric day and night drift velocities in the Taiwan sector. The scintillation data will be analyzed by the Hilbert-Huang Transform (HHT) method to decompose the time-series data into many intrinsic mode functions (IMFs) each contains a distinctive oscillation frequency (characteristic scale length) that can be inferred back to the irregularity structure that causes the dominant scintillation. The time-frequency spectragram obtained by the HHT analysis can reveal how irregularity structure changes with time. Any coincident observations with the AIP payload and the FORMOSAT-7/COSMIC-II (FS-7/COSMIC-II) GPS radio occultation (RO) data will help us understand the radiowave propagation characteristics from ionospheric irregularities. The high spatial resolution coverage of FS-7/COSMIC-II GPS RO data can also be used to obtain the global/seasonal scintillation maps during the ascending phase of solar cycle 25.The second part of the project is to construct a global/seasonal scintillation map using the recently launched FS-7/COSMIC-II GPS RO signals during the ascending phase of solar cycle of 25. The obtained global/seasonal scintillation maps will be used to compare with previously published scintillation maps constructed with FS-3/COSMIC data obtained in the decline phase of solar cycle 23. Comparing the two global/seasonal scintillation maps obtained at two different solar activity years will assist us to understand more about the solar flux effect on the occurrence of scintillation activity.The third part is to develop a near-real time ionosphere model TaiWan Ionosphere Model-2 (TWIM2) based on new FS-7/COSMIC-II GPS RO data. Accurate and precise real-time specification and modeling of the ionospheric electron density (Ne) are important to radio sky-wave communications and satellite navigation.The results of the study will be presented in the international scientific meetings such as the Fall AGU meeting and/or EGU scientific assembly first, and then written into papers to publish in scientific journals.