Observing-Systems Simulation Experiments: Past, Present, and Future

A summary of the history of observing-systems simulation experiments (OSSEs) is presented together with a description of current methodology, its capabilities and limitations, and considerations for the design of future experiments. These experiments are defined as a type of sensitivity study and are contrasted with real-data experiments otherwise known as observing-systems experiments (OSEs), data-impact, or data-denial experiments, which form a related type of sensitivity study. Simulation is presented as a means by which an a priori evaluation of proposed remote-sensing systems can be made.