1. Doctoral Fellow, Dept. of Aerospace Information Engineering, Konkuk Univ., 1 Hwayang-dong, Gwangjin-gu, Seoul 143-701, Korea.
2. Professor, Dept. of Aerospace Information Engineering, Konkuk Univ., 1 Hwayang-dong, Gwangjin-gu, Seoul 143-701, Korea (corresponding author).
3. Professor, Dept. of Aerospace Information Engineering, Konkuk Univ., 1 Hwayang-dong, Gwangjin-gu, Seoul 143-701, Korea.