Microwave Radiometers for Earth Observation from Space

We will follow the journey from the lab to Earth orbit of two NASA microwave radiometer instruments operating at extreme ends of both the radio spectrum and the mission risk class. The first is the Soil Moisture Active Passive (SMAP) microwave radiometer, which operates at 1.41 GHz (21 cm). SMAP is the first flagship mission developed in response to the 2007 National Academy of Sciences’ Earth science Decadal Survey. The SMAP radiometer continues to operate successfully in Low Earth Orbit (LEO) since 2015. The second is IceCube/Earth-1, which observes at 883 GHz (340 um) to measure ice clouds and is an Earth Science Technology Office tech-demo cubesat. Development of these scientific instruments started with a science need and an operational concept. Using SMAP and IceCube as examples, some of the engineering steps required to go from the low-level laboratory hardware to an on-orbit, calibrated radiometer will be described. Success ultimately entailed developing NASA technology, leveraging industry capability, suffering a fortuitous cancellation, and experiencing many laboratory successes and failures. Lessons from both instrument teams can be applied to future science and non-science radiometers alike.