SystemTime:

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   Provides the system time to the software.
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   Form:
   [mET, jD] = SystemTime( action, mET, jD )
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   ------
   Inputs
   ------
   action       (1,:) Action to take
   mET          (1,1) Mission elapsed time
   jD           (1,1) Julian Date

   -------
   Outputs
   -------
   mET          (1,1) Mission elapsed time
   jD           (1,1) Julian Date

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