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C-4.3 Command Processing and Transmition

Figure C-4 depicts the data flow for Process and Transmit Commands. Data originates in the Command Processing Product data store, which holds the command plan to be executed during contact. The Constraint DB data store provides constraint rules for each SV command. The Quality Assesed EU Measurands data store is used by Check Constraints to resolve any telemetry-related constraints. The constraint check status is written to the Command Status and History data store for post-pass analysis. If the command is a time-triggered command, then the Propagation Delay Times data store is read to determine the proper time to release the command so that it arrives at the SV at the desired time. The following describes the processes identified in Figure C-4.

Select Command for Transmission - This function executes the command plan, resulting in the generation of command elements. It inputs the command plan generated by Define Commands and Command Procedures. It may optionally input X-field entries, which are direct entries of commands from the satellite operator or command elements from external users.

Check Constraints - This function controls release of the command by determining if predefined constraints have been satisfied for each command element. It inputs the command element from Select Command for Transmission, telemetry data (Quality Assessed EU Measurands) to support constraint checks, and constraint rules for each command. Additionally, it inputs ground configuration status, including encryptor status, commanding rate, S-pulse status, and RGF command mode. The satellite operator may provide requests to inhibit constraints, clear commands from constraint checking, and enable requests for protected and restricted commanding. The function generates a command element when constraint conditions are satisfied, and generates transmission time for time triggered commands. It also outputs the command and ground status present when the constraint check conditions were satisfied. Note that if there is no constraint check for a particular command, the command element passes directly through to Transmit Command.

Figure C-4. Process and Transmit Commands data flow diagram.

Transmit Commands - This function transmits the command to the RGF. The process is part of the normal commanding sequence, or may be triggered by command retransmission requests from Determine Command Performance or the satellite operator. It may also process a request to halt transmission of the command stream. This function inputs the command element released from Check Constraints, the specified transmission times for time-triggered commands, and the propagation delay times to the satellite, the latter of which is used to determine the transmission time for time-triggered commanding. It takes as input the RGF status verifying correct status before transmission. The function generates a command stream (a sequence of bits of command elements) to the RGF/satellite or to the RGF/satellite simulator.