Eight commanding hardware architecture alternatives were determined based on commanding requirements and assumptions concerning technology projections and limitations. These eight architecture options, shown in Figure C-9, depict functional distribution across hardware platforms based on total performance load (resource sharing). Commanding functions are assigned to computing resources such as Commanding Front-End (CFE), server, and workstation (WS) in various combinations. The functions shown correspond to high-level functional components within the Commanding data flow diagrams as follows:
* Command Plan Execution - selection and execution of steps specified in the command procedure. This function is depicted in Figure C-4 as Select Command for Transmission.
* Constraint Check - evaluation of constraint rules for a command. This function is depicted in Figure C-4 as Check Constraints.
* Transmission - release of command to RGF. This function is depicted in Figure C-4 as Transmit Command.
* Verification - verification of the command execution. This function is depicted in Figure C-2 as Determine Command Performance.
* Display and X-term - input from and output to the SV operator. This function is depicted in Figure C-2 as Satellite Operator.
The following summarizes each alternative and the conditions under which each is desirable:
Option 1, [Max CFE (A)] - has all Commanding processes executing on the CFE. A workstation is used for user interface only. This option is desirable when high commanding rates, real-time multiconstraint command blocks, and real-time verification are required. It provides the fastest performance by eliminating delay time due to data transmission over a network.
Option 2, [Max CFE (B)] - is a slight variation of Option 1, with workstation display software executing on the workstation. This option reduces non-essential loading on the CFE.
Option 3, [CFE/Server (A)] - is a variation of Option 2, with the verification process executing on the server. This option is viable if there are real-time requirements for command constraint and transmission, but none for command verification.
Option 4, [WS/Server (B)] - is a variation of Option 2, with the command plan execution process executing on the server. This option has similar advantages to Option 2, but allows command plans to reside on a server platform for access by multiple operator workstations.
Option 5, [CFE/Server (C)] - is a variation of Option 3, with the verification process added to the server. This option is desirable if there are real-time requirements on command constraint and transmission, but none on command verification. It also allows command plans to reside on a server platform. This option is recommended for high commanding rates.
Option 6, [CFE/Server] - has all Commanding processes except transmission executed on the server and workstation. This option is desirable if there are no real-time requirements on the constraint check or the command verification processes. This configuration is supported by most commanding COTS products and is desirable for nominal commanding rates.
Option 7, [WS/Server] - is similar to Option 5, except that the server is replaced by a user workstation. This option is desired if workstations have enough processing power to include both commanding and display tasks.
Option 8, [Max WS (A)] - is similar to Option 6, except the server is replaced by a user workstation. This option is desired if workstations have enough processing power to include commanding, constraint checking, and display tasks. This option is also desirable for nominal commanding rates.
It was determined based on loading analysis that Option 5 would be best for high commanding rates, and Option 6 would be best for nominal commanding rates. However, option 5 would require separation of constraint check and verify functions, which is not supported by existing COTS products (see Command Software Architecture below).