Exposure Timings Reported in the LASCO/EIT Science Header

Here are the timelines for Normal and Cal Lamp Images (CAPS are actions, small are variables).

Normal Images

start time

SETUP

exp1

OPEN SHUTTER

exp2

EXPOSE

stop_time

CLOSE SHUTTER

exp3

CCD READOUT

ro_time

Differences are reported in the img header as:

header exp1 = exp1 - start_time

header exp2 = exp2 - exp1

header exposure_dur = stop_time - exp2

header exp3 = exp3 - stop_time

header ccd_readout = ro_time - exp3

Here is the IDL code that converts the raw header into FITS keywords:

exptime = h.exp_dur/32. IF (h.version GE 1) THEN exp123units = 2048. ELSE exp123units = 32. IF ((h.lp_num NE 5) AND (h.lp_num NE 7)) THEN exptime=exptime+h.exp3/exp123units ; ; 19 Mar 96: Correct for the 32 second jump in the absolute time, ; allowing for the temporary work around ; 01 Aug 96: Don't correct for obe header verison > 1 ; IF (h.version EQ 0) THEN $ IF ( abs(h.exp_dur-h.exp_cmd) GT 3 ) THEN exptime = exptime - 32. fxaddpar,fits,'EXPTIME',exptime fxaddpar,fits,'EXP0',h.exp_dur/32. fxaddpar,fits,'EXPCMD',h.exp_cmd/32. fxaddpar,fits,'EXP1',h.exp1/exp123units fxaddpar,fits,'EXP2',h.exp2/exp123units fxaddpar,fits,'EXP3',h.exp3/exp123units


Cal Lamp Images

C1 Door Lamp

C2 Door and Shutter Lamp

C3 Shutter Lamp

EIT Shutter Lamp

start time

SETUP

exp1

if DOOR_LAMP then OPEN SHUTTER

LAMP ON

exp2

EXPOSE

stop_time

LAMP OFF

if DOOR_LAMP then CLOSE SHUTTER

exp3

CCD READOUT

ro_time

Differences are reported in the header as:

header exp1 = exp1 - start_time

header exp2 = exp2 - exp1

header exposure_dur = stop_time - exp2

header exp3 = exp3 - stop_time

header ccd_readout = ro_time - exp3