Function: get_thm_esa_cal PURPOSE: Returns esa calibration factors INPUT: KEYWORDS: sc: string themis spacecraft - "a", "b", "c", "d", "e" if not set defaults to "a" ion: 0/1 0= electron esa, 1= ion esa, default=0 time: dblarr times that relative geometric factor are to be returned CREATED BY: J. McFadden VERSION: 1 LAST MODIFICATION: 07/07/08 MOD HISTORY: NOTES: