I’m in the Global Modeling and Assimilation Office (GMAO). As a group, we model the Earth’s system: the atmosphere, the ocean, the land surface, the ice sheets, and how they all interact. As a part of that, we ingest observations, including satellite observations, into our modeling systems through a process called data assimilation. In effect, we combine modeled physics with observations to produce the best representation possible of what has happened and is happening in the real world. The Earth states we produce have many potential uses. They can serve, for example, as starting points for weather forecasts. I personally contribute to the land modeling and hydrology (the study of Earth’s water) component of this overall effort.