Weather poses significant economic, safety, and national security challenges to our military and civilian populations. As such, the US Airforce has commissioned Ball Aerospace to build the Next-generation defense weather satellite system. This system will require accurate measurements of top-of-atmosphere brightness temperatures to determine ocean surface vector winds, tropical cyclone intensity, and other environmental products necessary to support our warfighters. At Ball, we have built the Global Precipitation Measurement (GPM) Microwave Imager (GMI) designed to be the radiometric calibration standard for a group of national and international passive microwave instruments in the GPM constellation. Ball and Remote Sensing Systems supported the initial on-orbit operations to verify calibration performance and provide a final set of operational calibration algorithms. The GMI instrument was launched onboard the GPM spacecraft on February 28th, 2014. GMI has operated nearly continuously since March 4th, 2014. This paper presents GMI’s on-orbit performance and calibration results and provides a top-level overview of how the GMI can be leveraged for next-generation defense weather missions.