Status of Studies on the Geostationary Precipitation Radar Satellite

The Global Precipitation Measurement (GPM) mission aims to provide precipitation data at anywhere on the earth every three hours. JAXA and NASA has developed the GPM core satellite, launched on Feb 27th, 2014, and started the measurement. Although the mission is successfully going, more precipitation measurement is requested beyond the GPM mission, such as identification of typhoon characteristics and its forming process, in which higher time resolution is needed. As one of the satellites that can meet the requirement, JAXA kicked off the investigation of the Geostationary Precipitation Radar (GPR) satellite. Considering the assumed mission requirement at the moment, the GPR has to have over 30m square antenna. On the other hand, JAXA is studying the Space Solar Power Systems (SSPS) and has been researching automatic construction technologies for large space structures because the typical microwave-based SSPS require few km square phased array antennas for transmitting the electric power to the earth. Therefore, we have been studying the feasibility of the GPR while using the research results of the automatic construction technologies. We set tentative mission requirements in consideration of user’s needs and have carried out a conceptual study on the electric system of the GPR so far. We also devised a construction method for the 30-m-class large phased array antenna and demonstrated the concept by carrying out a ground experiment.