Catching whales has long been discussed internationally among the specialists and organizations concerned. The ecology of whales, however, is not sufficiently clear yet. Since Japan has been assigned at the International Whale Committee as the responsible country for monitoring ecology of blue whales in the antarctic ocean, we have started a study on a Whale Observation Satellite System. This system comprises of three elements: a small satellite on a polar orbit, ecological sensor probes attached to whales, and a ground station. In each probe, a receiver of GPS, several sensors to collect ecological data of a whale, a memory to record the sensor data collected, a UHF transmitter, antennas and a power generator are installed. When the whale and the probe come up to the sea surface, the GPS receiver will locate the position of the probe. The electric power needed for the probe is generated by utilizing the motion of the whale. The electric power is generated by a stack of kinetic power generator units, which will be practically applied to a wristwatch. The position data together with the ecological data are sent to the satellite on a polar orbit of 800 ~ 1300 km high, which has been an elongated structure with a deployed mast, and its attitude is controlled by gravity gradient torque. The antennas fixed at the end of the satellite body will point the earth, and communication link will be established. The satellite stores the data sent from probes in a memory on board. When the satellite flies over the ground station, the station will send a command signal to the satellite, and all the data in the memory are sent back to the earth. Thus ecological data and migratory patterns of whales will be obtained
