R&D status of the next generation optical communication terminals in JAXA

Optical free space communication is a key element of the future data-relay satellite system which supports space activities, especially in the fields of earth observation satellite programmes and manned flight missions. Aiming to realization of small and light-weight onboard optical terminals, JAXA launched research and development activities in 2008. The terminals have capabilities to enable communication links up to 2.5 Gbps between data relay satellites in GEO and LEO earth observation satellites. The target weights of terminals are less than 35 kg for LEO terminal and less than 50 kg for GEO terminal, respectively. In this paper, the current status and outcomes of R&D toward JAXA's next generation optical communication system are reported. The system design of the terminals and studies of critical technologies which are necessary to realize the terminals are performed. As a study of critical technology, a homodyne coherent optical receiver has been developed and successfully operated under Doppler optical carrier shift which is unenviable in GEO-LEO communication links. In addition, JAXA's efforts toward to establish future data relay satellite system are also presented.