VHF radio observations of lightning discharges on JEM-GLIMS

Since 2012, the global lightning and sprite measurements (GLIMS) mission has been conducted on the exposed facility of Japanese experiment module (JEM-EF) of the international space station (ISS). In this mission, the VHF broadband digital interferometer (VITF) attached on JEM-EF is designed to estimate the direction of arrival of electromagnetic waves. The VITF has the bandwidth from 70 MHz to 100 MHz. The electromagnetic radiations from lightning discharges received by two antennas are digitized by the 2-channel AD converter. We introduce the outline of the mission and the VITF. The initial observational results with the VITF of the GLIMS mission are presented. The comparison of the results of arrival direction estimation of the VITF with optical observations using two methods which are an interferometry technic and the group delay characteristic of EM waves. The results agree with the position of the lightning emission captured by the LSI.