GPM is a joint mission with Japan. The Japanese space agency, JAXA, has provided the primary science instrument, the Dual frequency Precipitation Radar, and the launch vehicle. This is the same arrangement we had with Japan for GPM's predecessor, TRMM, the Tropical Rainfall Measuring Mission. Besides the primary goal of better understanding the processes that drive our planet's weather there is the secondary goal of fostering international scientific cooperation.
Please do not confuse launch services with space exploration. NASA hasn't directly been in the commercial launch service since the dawn of the space age was over. Commercial satellite operators contract directly with commercial launch providers such as ULA, Orbital, Space-X, Arianespace or ILS.
I am in complete agreement with your point about lack of political support for space science and exploration. While there has been no real support for space exploration for decades, the past decade has seen a real drop in actual support (that is, money) for space science. I suspect that is true for science in general, but space is my business.