CALACS¶

CALACS Python Wrapper¶

The calacs module contains a function calacs that calls the CALACS executable. Use this function to facilitate batch runs of CALACS.

Examples

>>> from acstools import calacs
>>> calacs.calacs(filename)

For help usage use exe_args=['--help']

Functions¶

calacs(input_file[, exec_path, time_stamps, …])

Run the calacs.e executable as from the shell.

ACSCCD Python Wrapper¶

The acsccd module contains a function acsccd that calls the ACSCCD executable. Use this function to facilitate batch runs of ACSCCD.

Note

Calibration flags are controlled by primary header.

Warning

Do not use with SBC MAMA images.

Examples

>>> from acstools import acsccd
>>> acsccd.acsccd('*raw.fits')

For help usage use exe_args=['--help']

Functions¶

acsccd(input[, exec_path, time_stamps, …])

Run the acsccd.e executable as from the shell.

ACSCTE Python Wrapper¶

The acscte module contains a function acscte that calls the ACSCTE executable. Use this function to facilitate batch runs of ACSCTE.

Only WFC full-frame and some 2K subarrays are currently supported. See ACS Data Handbook for more details.

Note

Calibration flags are controlled by primary header.

Examples

>>> from acstools import acscte
>>> acscte.acscte('*blv_tmp.fits')

For help usage use exe_args=['--help']

Functions¶

acscte(input[, exec_path, time_stamps, …])

Run the acscte.e executable as from the shell.

ACSREJ Python Wrapper¶

This module contains a function acsrej() that calls the acsrej.e executable. Use this function to facilitate batch runs of ACSREJ.

Examples

>>> from acstools import acsrej
>>> acsrej.acsrej('*flt.fits', 'combined_image.fits')

For help usage use exe_args=['--help']

Functions¶

acsrej(input, output[, exec_path, …])

Run the acsrej.e executable as from the shell.

ACS2D Python Wrapper¶

The acs2d module contains a function acs2d that calls the ACS2D executable. Use this function to facilitate batch runs of ACS2D.

Examples

>>> from acstools import acs2d
>>> acs2d.acs2d('*blv_tmp.fits')

For help usage use exe_args=['--help'].

Functions¶

acs2d(input[, exec_path, time_stamps, …])

Run the acs2d.e executable as from the shell.

ACSSUM Python Wrapper¶

The acssum module contains a function acssum that calls the ACSSUM executable. Use this function to facilitate batch runs of ACSSUM.

Examples

>>> from acstools import acssum
>>> acssum.acssum('*flt.fits', 'combined_image.fits')

For help usage use exe_args=['--help']

Functions¶

acssum(input, output[, exec_path, …])

Run the acssum.e executable as from the shell.

CTE Forward Model¶

This functionality is provided but not run as part of the pipeline.

The acscteforwardmodel module contains a function acscteforwardmodel that calls the ACSCTE forward model executable. Use this function to facilitate batch runs of the forward model.

Only WFC full-frame and some 2K subarrays are currently supported. See ACS Data Handbook for more details.

For guidance on running the CTE forward model, see the Jupyter notebook ACS CTE Forward Model Example.

Note

Calibration flags are controlled by primary header.

Examples

>>> from acstools import acscteforwardmodel
>>> acscteforwardmodel.acscteforwardmodel('*blc_tmp.fits')

For help usage use exe_args=['--help']

Functions¶

acscteforwardmodel(input[, exec_path, …])

Run the acscteforwardmodel.e executable as from the shell.

PIXVALUE in FITS File¶

CALACS uses HSTIO that utilizes PIXVALUE keyword to represent a data extension with constant value. However, this is not a standard FITS behavior and is not recognized by astropy.io.fits. Therefore, one should use stsci.tools.stpyfits, which is distributed as part of stsci_python, instead of astropy.io.fits when working with CALACS products. To use stpyfits in Python:

from stsci.tools import stpyfits as fits

calacs.e (C Program)¶

A detailed description of this new and improved CALACS is available in ACS Data Handbook v7.0 or later. If you have questions not answered in the documentation, please contact STScI Help Desk.

Where to Find CALACS¶

CALACS is now part of HSTCAL package.

Usage¶

From the command line:

calacs.e jb1f89eaq_raw.fits [command line options]

Command Line Options¶

CALACS supports several command line options:

-t
- Print verbose time stamps.
-s
- Save temporary files.
-v
- Turn on verbose output.
-d
- Turn on debug output.
-q
- Turn on quiet output.
-1
- Turn off parallel processing for PCTECORR. Try this option if you encounter problems running CALACS with PCTECORR=PERFORM.
--nthreads <N>
- Specify the number of threads used for PCTECORR. The default is ‘greedy’ and will use that specified by the system environment variable OMP_NUM_THREADS. If N > OMP_NUM_THREADS, OMP_NUM_THREADS will be used instead. The option -1 takes precedence.
--ctegen <1|2>
- Specify which generation CTE correction to use, the default is 2. Gen 1 (officially deprecated) refers to the correction algorithm used in calacs version pre 9.2.0 in relation to the following ISRs ACS ISR 2010-03 and 2012-03. Gen 2 refers to the new CTE correction algorithm implemented in calacs version 9.2.0 (HSTCAL 1.3.0) in relation to the ISR (to be updated).
--pctetab <filename>
- Override the PCTETAB reference file specified in the image header.

Parallel Processing with OpenMP¶

By default, CALACS will attempt to perform PCTECORR using all available CPUs on your machine. You can set the maximum number of CPUs available for CALACS by either using the command line option –nthreads <N> or by setting the OMP_NUM_THREADS environmental variable.

In tcsh:

setenv OMP_NUM_THREADS 2

In bash:

export OMP_NUM_THREADS=2

Batch CALACS¶

The recommended method for running CALACS in batch mode is to use Python and the acstools package.

For example:

from acstools import calacs
import glob

for fits in glob.iglob('j*_raw.fits'):
    calacs.calacs(fits)

CALACS Processing Steps¶

BIASCORR¶

BIASCORR is now performed before BLEVCORR. This should not significantly affect science results. This change was necessary to accomodate BIASFILE subtraction in DN with the rest of the calculations done in ELECTRONS.

Unit Conversion to Electrons¶

The image is multiplied by gain right after BIASCORR, converting it to ELECTRONS. This step is no longer embedded within FLATCORR.

BLEVCORR¶

BLEVCORR is now performed after BIASCORR. Calculations are done in ELECTRONS.

For post-SM4 full-frame WFC exposures, it also includes:

de-striping to remove stripes introduced by new hardware installed during SM-4 (J. Anderson; ACS ISR 2011-05); and
if JWROTYPE=DS_int and CCDGAIN=2, also correct for bias shift (ACS ISR 2012-02) and cross-talk (N. Grogin; ACS ISR 2010-02).

SINKCORR¶

SINKCORR flags sink pixels and the adjacent affected pixels with the value 1024 in the DQ array of WFC images using the SNKCFILE. Only performed on images taken after January 2015.

Pixel-Based CTE Correction (PCTECORR)¶

For all full-frame WFC exposures, pixel-based CTE correction (ACS ISR to be updated) is applied in ACSCTE that occurs after the ACSCCD series; i.e., after BLEVCORR.

Because the CTE correction is applied before DARKCORR and FLSHCORR, it is necessary to use a CTE-corrected dark (DRKCFILE) if the PCTECORR step is enabled.

Parameters characterizing the CTE correction are stored in a reference table, PCTETAB.

Note

CALACS 8.2 and later uses a slightly different PCTETAB format, where the COL_SCALE extension does not include overscan columns.

Required Keywords¶

Running CALACS with pixel-based CTE correction requires the following header keywords:

PCTECORR
- By default, set to PERFORM for all full-frame WFC exposures, except BIAS.
PCTETAB
- Reference table containing CTE correction parameters. By default, it should be in the jref directory and have the suffix _cte.fits.
DRKCFILE
- Similar to DARKFILE but with CTE correction performed. By default, it should be in the jref directory and have the suffix _dkc.fits. This is necessary because PCTECORR is done before DARKCORR.

Optional Keywords¶

You may adjust some CTE correction algorithm parameters by changing the following keywords in the RAW image header. The default values are picked for optimal results in a typical WFC full-frame exposure. Changing these values is not recommended unless you know what you are doing.

FIXROCR
- Account for and correct readout cosmic ray over-subtraction.
  0 - Off: do not correct
  
  1 - On: correct
PCTENPAR
- Number of parallel transfer iterations.
PCTENSMD
- Read noise mitigation mode:
  0 - No mitigation
  
  1 - Perform noise smoothing
  
  2 - No noise smoothing
PCTERNOI
- Read noise amplitude in ELECTRONS.
PCTETLEN
- Maximum length of CTE trail.
PCTENFOR
- Number of iterations used for forward CTE model.

Dark Current Subtraction (DARKCORR)¶

It uses DARKFILE if PCTECORR=OMIT, otherwise it uses DRKCFILE (CTE-corrected dark reference file).

Dark image is now scaled by EXPTIME and FLASHDUR. For post-SM4 non-BIAS WFC images, extra 3 seconds are also added to account for idle time before readout. Any image with non-zero EXPTIME is considered not a BIAS.

Post-Flash Correction (FLSHCORR)¶

Post-flash correction is now performed after DARKCORR in the ACS2D step. When FLSHCORR=PERFORM, it uses FLSHFILE.

FLATCORR¶

Conversion from DN to ELECTRONS no longer depends on FLATCORR=PERFORM. Unit conversion is done for all exposures after BIASCORR.

Photometry Keywords (PHOTCORR)¶

The PHOTCORR step is now performed using tables of precomputed values instead of calls to SYNPHOT. The correct table for a given image must be specified in the IMPHTTAB header keyword in order for CALACS to perform the PHOTCORR step. By default, it should be in the jref directory and have the suffix _imp.fits. Each DETECTOR uses a different table.

If you do not wish to use this feature, set PHOTCORR to OMIT.

CALACS Output¶

Using RAW as input:

flt.fits: Same as existing FLT.
flc.fits: Similar to FLT, except with pixel-based CTE correction applied.

Using ASN as input with ACSREJ:

crj.fits: Same as existing CRJ.
crc.fits: Similar to CRJ, except with pixel-based CTE correction applied.