Figure A-4 describes the DFD associated with the Plan Orbital Maneuvers process. The Orbit Ephemeris, Attitude Ephemeris, and Quality Assessed EU Measurands data stores provide data needed to evaluate the current state and health of the vehicle (see Figure A-2, the overall DFD for Mission Planning). The Mission Planning Requirements data store, shown in Figure A-2, describes mission requirements, objectives, and constraints on orbital maneuvers. The text below describes the data flow for Plan Orbit Maneuvers.
Evaluate Vehicle State - This process accepts as input the desired orbit state along with the orbit maneuver planning activity. It then performs monitoring and assessment of the spacecraft's orbital and attitude state as well as the health and status of on-orbit subsystems via telemetry. Key among these parameters will be status of on-board propellant, mass properties, power balance, and thermal management subsystems. The need for an attitude maneuver before the orbital maneuver is also assessed. If needed, a maneuver to assume the required attitude is requested through the Timeline data store.
Generate Maneuver Parameters - Based on the vehicle's state and existing requirements and constraints on maneuvers, this process determines the parameters for executing an orbital maneuver (delta V magnitude, burn duration, commands and burn epoch). These parameters are stored in the Orbit Maneuver Parameters data store for use by other applications. Prediction of the post-maneuver vehicle state is also performed and recorded.