imap_processing.idex.idex_l1a.calculate_idex_epoch_time

imap_processing.idex.idex_l1a.calculate_idex_epoch_time(shcoarse_time: float | ndarray, shfine_time: float | ndarray) → ndarray[tuple[int, ...], dtype[int64]]

Calculate the epoch time from the FPGA header time variables.

We are given the MET seconds, we need to convert it to nanoseconds in j2000. IDEX epoch is calculated with shcoarse and shfine time values. The shcoarse time counts the number of whole seconds elapsed since the epoch (Jan 1st 2010), while shfine time counts the number of additional 20-microsecond intervals beyond the whole seconds. Together, these time measurements establish when a dust event took place.

Parameters:

• shcoarse_time (float, numpy.ndarray) – The coarse time value from the FPGA header. Number of seconds since epoch.

• shfine_time (float, numpy.ndarray) –

  The fine time value from the FPGA header. Number of 20 microsecond “ticks” since

  the last second.

Returns:

The mission elapsed time converted to nanoseconds since the J2000 epoch in the terrestrial time (TT) timescale.

Return type:

numpy.ndarray[numpy.int64]