Development of small optical transmitter for microsatellites

In this paper the small optical transmitter for microsatellite which is now under development is described. In recent years, the amount of downlink data is increasing and the faster speed communication system has been required. Therefore the optical communication which can realize the high data rate transmission by far than conventional radio waves has been attracting attention. However the high precision pointing is required in optical communication. Although conventional optical communicators of large satellites have been achieving high pointing accuracy by mechanical gimbal and movable pointing mirror, this type optical communicator would occupy a high proportion of mass and power resources of microsatellites. Then the optical transmitter without mechanical gimbal which points to the target by the Attitude Control System (ACS) of the satellite was proposed. Optical communicator of this method can be very compact and can be mounted on microsatellites. However initial discovery by ground station communicator is difficult in this method. For this reason the adjustable beam spread angle type was adopted in desired optical transmitter. The beam divergence from this transmitter can be expanded and initial discovery will be easy. The status of development is test model. The behavior of received light was analyzed in simulation and receive gain of more than - 40 dBm.