Space Telescope Imaging Spectrograph
CL Script for Correcting Exposure Times Affected by Take Data Flag Down

Download the script

The "fixtime" script requires two input files and a flag enabling update:

1. The raw data file (*_raw.fits);
2. The support information file (*_spt.fits).
3. A "yes" or a "no" indicating whether you wish to enable updating the header

The script reads the nominal exposure time for each imset in the raw data file. From the support file it gathers the necessary information to calculate the length of time the "Take Data Flag" was down during each imset. This correction is applied to the exposure times for each imset. If you have enabled updates with a "yes" on the command line, the header of the raw data file is updated. The script prints summary information on the exposure time corrections to the screen. After running the script on the raw data file, you will need to re-run calstis in the stsdas.hst_calib.stis package in IRAF.

To use the script in IRAF, follow this example:

set ft=osfn('.')
task fixtime = ft$fixtime.cl
fixtime don1_raw.fits don1_spt.fits yes

Correcting don1_raw.fits using don1_spt.fits
Original Total Exposure Time is 2700.
 
    Planned  exposure time for  imset 1 is 1349.9999993714
    Exp start: 51045.92627214
    TDF  down: 48005.970782699
    TDF    up: 48005.970782699
    Exp   end: 51045.94189714
    Corrected exposure time for imset 1 is 1349.9999993714
 
    Planned  exposure time for  imset 2 is 1349.9999993714
    Exp start: 51045.94240659
    TDF  down: 51045.94619844
    TDF    up: 51045.947761032
    Exp   end: 51045.95803159
    Corrected exposure time for imset 2 is 1214.9919991381
 
Corrected total exposure time is 2564.9919985095

Download the script