This chapter describes the methods and techniques for designing mission operations systems (MOS) for spacecraft remote sensing within a context of standard programmatic steps and documentation used by both the National Aeronautics and Space Administration and industry. When a hardware component is built, documents proceed from requirements specifications to design specifications to procurement description documents to as-built, end-item specification documents for the hardware configuration. The MOS design requirements document will specify how the mission and science requirements will be converted to operations requirements to achieve implementation of the spacecraft operations control activity. Functional analysis used in conjunction with an operations concept provides an organized representation of a system against which to specify and evaluate design requirements. One important consideration when designing data flow diagrams is to avoid drawing lines which represent organizational structure or communication lines that follow paths between organizational entities.