Procedure: THM_CAL_FFT Purpose: Converts raw FFT (on-board FFT spectra) data into physical quantities. keywords: probe = Probe name. The default is 'all', i.e., calibrate data for all available probes. This can be an array of strings, e.g., ['a', 'b'] or a single string delimited by spaces, e.g., 'a b' datatype = The type of data to be loaded, 'ffp_16', 'ffp_32', 'ffp_64', 'ffw_16', 'ffw_32', or 'ffw_64'. default is 'all', to calibrate all variables. due to some last minute changes it is required that you include both the raw and the calibrated datatype you want for this function to perform properly in_suffix = optional suffix to add to name of input data quantity, which is generated from probe and datatype keywords. out_suffix = optional suffix to add to name for output tplot quantity, which is generated from probe and datatype keywords. /VALID_NAMES; returns the allowable input names in the probe and datatype variables /VERBOSE or VERBOSE=n ; set to enable diagnostic message output. higher values of n produce more and lower-level diagnostic messages. Example: thm_cal_fft Notes: -- Changes between signal sources are handled; source info from HED data should be used to get actual units of a given spectrum. -- fixed, nominal calibration pars used (gains and frequency responses), rather than proper time-dependent parameters.