The first in a series of Earth observation satellites created by the Japan Aerospace Exploration Agency and designed to examine global water circulation and climate change from space. The 1 900 kg spacecraft (then known as Shizuku) launched from Tanegashima Space Centre on 18 May 2012 and joined the A-Train about a month later. The satellite employs an advanced microwave scanning radiometer for observing water circulation changes from a Sun-synchronous orbit.