Feasibility Study of Laser Communications on International Space Station

We are designing the Laser Communications Demonstration Equipment (LCDE) attached to the Japanese Experiment Module “Kibo” on the International Space Station (ISS), for laser communications experiments between the ISS and ground stations. The experiment will demonstrate large-capacity, high-data-rate (2.5 Gbps) two-way communications. A preliminary experiment to detect space debris will also be performed. In the first stage of the experiment, it is necessary to track geodetic satellites and to compensate the optical misalignment of the LCDE in order to achieve precise tracking and pointing. Sunlight reflected from geodetic satellites will be used for tracking. This provides the tracking angle information. As the received power is very low (about - 95 dBm), a sensitive tracking sensor is needed. This paper summarizes the LCDE, studies on the visibility of the geodetic satellites from the ISS, and the tracking performance includingthe sensitivity of the sensor.