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   The spacecraft clock is the onboard time-keeping mechanism that triggers
   most spacecraft events, such as shuttering of a camera. Since telemetry
   data are downlinked with this clock's time attached to it, spacecraft
   clock time (SCLK--pronounced ``s-clock'') is the fundamental time
   measurement for referencing many spacecraft activities.
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   It is natural, then, that SCLK have an important role in the CSPICE
   system. In fact, all C-kernel pointing data are referenced to SCLK.
  