1. Mitsubishi Electric Corporation, Advanced Technology R&D Center, 8-1-1 Tsukaguchi Honmachi, Amagasaki, Hyogo 661, Japan
2. The Institute of Space and Astronautical Science (ISAS), 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229, Japan
3. A'Iitsubishi Electric Corporation, Kamakura Works, Kami-Machiya, Kamakura, Kanagawa 247, Japan