Globalization extension of transient luminous events from FORMOSAT-2 observation

Abstract

Since its launch on 20 May 2004, FORMOSAT-2 (FS2) is still the unique satellite to observe the transient luminous events (TLEs) from orbit. In nearly 9 years from 4 July 2004 to 31 May 2013, the number and distribution of TLEs observed are summarized. The instrument used for the observation of TLEs is called imager of sprites and upper atmospheric lightning (ISUAL). This is the first time the observation results are presented in the International Astronautical Congress (IAC). Due to the orbital characteristics of FORMOSAT-2, unobserved gaps exist between each two orbits. Also, the ISUAL has its detection threshold. In this paper, besides the presentation of above results, globalization extension of TLEs is performed based on FORMOSAT-2׳s observation. Factors considered include number of orbits ISUAL in operations, daytime and night-time, season, non-observed areas, observability of TLEs, limb view hiding, and other factors. An estimated global occurrence rate is 24TLEs/min, but this number is still much less than the possible potential rate of 195. To enhance the results, more instruments and longer observation time are required.