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C-4.1 Commanding - Top Level

Figure C-2 depicts the top-level data flow diagram for the Commanding function. The Command Requirements data store contains vehicle-specific high-level commanding requirements needed by Define Commands and Command Procedures to generate lower-level data items to support Commanding. This information includes formatting rules, contingency conditions, verification methods, and fault recovery methods. The Vehicle Command Word Structure data store contains the actual command structure for each SV command. The Timeline data store contains all command activities, each of which is the specification of a commanding task in the form of a pass plan. The command activity is typically specified by Mission Planning but can also be specified by Commanding or Telemetry. The Command Processing Product data store contains the command plan (the sequence of commands to be uploaded to the SV during the contact). This plan is read by Process and Transmit Commands to generate Command Streams. The Command Processing Product data store also contains command history and status information. The Quality Assessed EU Measurands data store contains the SV decoder state, authentication, and SV state telemetry. This data is used by Determine Command Performance to evaluate commands. The following describes the processes identified in Figure C-2.

Define Commands and Command Procedures- This function generates command data stores that are used to support command processing. It takes as input the command word structure and the command requirements that are derived by the vehicle contractor. This function also takes as input the command activity, which is a commanding task specification that is identified in a pass plan within the Timeline data store. In addition, any recommended corrective actions are input from Process Telemetry or Determine Command Performance to resolve SV anomalies in real time. This function generates a set of vehicle specific databases and command plans to support the command activities, which are contained in the Command Processing Product data store.

Process and Transmit Commands - This function performs the necessary processing to transmit commands to the Communications and Range Segments. The primary input is command plans created in Define Commands and Procedures. In addition, this function accepts the vehicle state from Process Telemetry to support telemetry-triggered commanding. This process also inputs ground system configuration to support ground status constraint checking and RGF status to check for successful command transmission. Finally, this function inputs requests for command retransmission from Determine Command Performance if it determines that the command requires retransmission. This function outputs the command stream (a sequence of command elements) to the RGF, which transmits the stream on to the satellite. This function can also generate a command stream to the vehicle TT&C simulator. In addition, it outputs information about the command transmitted, commanding status, and ground status, which are stored in a command history database.

Figure C-2. Overall data flow diagram for Commanding.

Determine Command Performance - This function performs analysis of command performance using command history, ground status history, and telemetry data. It generates command performance status for the satellite operator and, if necessary, a request for command retransmission for some types of command failures. This function can also generate a recommended corrective action plan for resolving certain commanding anomalies in real time. In addition, this function is responsible for generating SOH activity requests and placing them in the Timeline data store as unknown and non-real-time corrective action requests for Mission Planning to schedule.

Define Commanding Data - This function provides the vehicle contractor or engineer the ability to input and modify mission-unique command requirements and vehicle command word structure. This function generates the data stores for SV command requirements and command word structure. In addition, it generates specific memory uploads that may be needed.

Configure System - This function provides the current ground configuration status to Process and Transmit Commands.