I just got my ACS data. What are all these files?
How can I quickly display my science data?
If you are unfamiliar with ACS file formats and
naming conventions, it can be a bit confusing at
first to sort out which files you really need,
which you might be able to delete, and how to
begin working with your ACS data.
The following files are the most critical, but
depending on your data reduction plans
(see below), you probably only need a subset
of them:
*_asn.fits (association tables; relate CR-SPLIT or dithered data)
*_raw.fits (raw images used to generate all of the following)
*_flt.fits (flat-fielded images; multidrizzle input)
*_crj.fits (cosmic-ray cleaned/combined images; PyDrizzle input)
*_drz.fits (distortion corrected PyDrizzle output in e/sec)
Note that the science data (sci), data quality
(dq), and error (err) arrays are stored in FITS
extensions within these files. The drizzled files
(*drz.fits) include weight (wht) and context (ctx) extensions.
In IRAF, use tprint to see the contents of association tables,
and catfits to see all the FITS extensions.
To quickly examine your files, and display the science array
in any of the images above:
cl> tprint *asn.fits
cl> catfits *_drz.fits
cl> display *_drz.fits[sci,1] zr+ zs+
These files may or may not be immediately
(or ever) useful to you:
*_sfl.fits (calibrated REPEAT-OBS combined image)
*_trl.fits (CALACS trailer file; logs each step)
*_spt.fits (telemetry and engineering data)
Your calibration reference files may also be present,
if you requested them. The "best" reference
files are typically available 2-3 weeks after
your observation date, e.g. the dark reference
file (for your particular observation date)
takes some time to produce.
If you plan to recalibrate your data
(re-run CALACS), you only need the raw
files (*raw.fits),
the best reference files, and the association
tables (*asn.fits) that CALACS needs as input.
Alternately, you could just wait 2-3 weeks after
your observation date
(until the best reference files are in place
in the calibration pipeline), and then
re-request your data via on-the-fly-reprocessing
(OTFR).
If you plan to re-run PyDrizzle, the
cosmic-ray cleaned images (*crj.fits)
will be needed as input.
If want to run multidrizzle, you will need the
flat-fielded images (*flt.fits) as input. If they don't
already exist, you will need to
set EXPSCORR=PERFORM in your raw image headers
and re-run CALACS to generate them.
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