function hsi_timebin_evaluator,calibeventlist
;+
; NAME: hsi_timebin_evaluator
;
; PURPOSE:
; To determine whether the HESSI modulation is undersampled
;
; INPUTS:
;   calibrated event list structure
;
; OUTPUTS:
;    Returns the number of indices per minimum cycle period, and
;    if this is LT 2, prints a warning message.
; 
;  EJS Dec 16, 1999
;
; Find the parameters of the modulation frequency 
;-

  roll=calibeventlist.roll_angle
  phase_map_ctr=calibeventlist.phase_map_ctr
  amp_pha=ls_sin_cos(roll,phase_map_ctr,1.0,yfit,sigma,/amp_pha)

  rmin_cycle_period=2*!pi/amp_pha[0]         ;=pitch/R  (radians)
  imin_cycle_period=rmin_cycle_period*N_elements(roll)/(max(roll)-min(roll))    ;  (indices)
  
if imin_cycle_period LT 2 then begin
    min_angle_bin=(max(roll)-min(roll))*2/rmin_cycle_period
    message,'WARNING: shortest cycle_period='+string(imin_cycle_period)+' time bins',/info
    message,'         You need at least'+strcompress(fix(min_angle_bin))+' angle bins',/info
endif

return,imin_cycle_period

end