The Chung-Li VHF radar as a meteor radar: System phase bias estimation and experimental results

A new scheme of processing radar returns was developed at the Chung-Li VHF radar to estimate the radar system phase bias that is inherently induced by the phase imbalance between receiving channels and hard to determine using conventional methods. With the help of IGRF95 model, echoes from 3 m field-aligned ionosphere sporadic E (Es) irregularities have been used successfully to estimate system phase bias of the ionospheric array of the Chung-Li VHF radar. In an analogous manner, the system phase bias of the interferometer array designed to detect meteor echoes is also determined by comparing observed and expected echoing region of Es field-aligned irregularities. The results show that the system phase bias is about 60° between receiving channel pair 1 and 2, and is about 39° between receiving channel pair 3 and 2. After removing the system phase biases, correct angle of arrival of the meteor echoes detected by interferometer array of the Chung-Li VHF radar can be determined unambiguously. The experimental result shows that most meteor echoes distribute within the region illuminated by the main lobe of the antenna beam, not from the sidelobe. Plasma diffusion coefficient and tidal wind in the mesosphere are also measured from radar returns generated from underdense meteor trails associated with the Leonid Meteor Shower during the period from November 13-19, 1997. We find that the height variation of the diffusion coefficient D follows the expression h = 78.84 + 8.59(InD), very similar to those obtained by other investigators. The mesospheric wind over the Chung-Li radar site is found to be dominated by diurnal tide superimposed by weak semi-diurnal tide. Analysis indicates that the tidal mode responsible for the diurnal tide seems to be S¹₁ mode.