BackPrep

BackPrep - Background Preparation using SWarp.

Space Telescope Science Institute

Synopsis

Create background images from DECam data using SWarp for improved source detection and photometry.

Command Line Usage

Basic usage::

BackPrep.py [-all] [-setup] [-run] [-indir directory] field tile

Arguments
^^^^^^^^^

field : str
Field name (e.g., 'LMC_c42')
tile : str
Tile identifier (e.g., 'T07')

Options
^^^^^^^

-all
Process all tiles found for the specified field
-setup
Only set up SWarp configuration files without running (default behavior)
-run
Set up and execute all SWarp commands
-redo
Regenerate background files even if they already exist
-indir directory
Use a different input directory (e.g., 'DECam_PREP2' for diagnostics).
Outputs will be placed in a 'XXX' subdirectory.

Description

BackPrep.py performs two main tasks:

Setup mode (default): Creates SWarp configuration files and run scripts for background image generation without executing them.
Run mode (with -run): Sets up configuration files and executes all SWarp commands to generate the background images.

The module processes astronomical images organized by field and tile, creating resampled background images that can be used for background subtraction and source matching.

Version History

230504 ksl: Coding begun

Examples

Set up SWarp for a single tile:

$ python BackPrep.py LMC_c42 T07

Set up and run SWarp for a single tile:

$ python BackPrep.py -run LMC_c42 T07

Process all tiles in a field:

$ python BackPrep.py -all -run LMC_c42

Use a custom input directory:

$ python BackPrep.py -indir DECam_PREP2 -run LMC_c42 T07

Version History

230504 ksl

Coding begun

Examples

Set up SWarp for a single tile:

$ python BackPrep.py LMC_c42 T07

Set up and run SWarp for a single tile:

$ python BackPrep.py -run LMC_c42 T07

Process all tiles in a field:

$ python BackPrep.py -all -run LMC_c42

Use a custom input directory:

$ python BackPrep.py -indir DECam_PREP2 -run LMC_c42 T07

Attributes

`PREPDIR`
`SWARPDIR`
`default`
`exec_dir`

Functions

`create_swarp_dir`([field, tile])	Create a directory for SWarp outputs if it does not exist.
`prep_one_tile`([field, tile, redo])	Prepare SWarp configuration and run script for one tile.
`run_back`([field, tile])	Execute SWarp for background field processing.
`steer`(argv)	Parse command-line arguments and coordinate BackPrep operations.

Module Contents

BackPrep.PREPDIR = b'.'

BackPrep.SWARPDIR = 'DECam_BACK'

BackPrep.create_swarp_dir(field='LMC_c42', tile='T07')

Create a directory for SWarp outputs if it does not exist.

Parameters

fieldstr, optional: Field name. Default is ‘LMC_c42’.
tilestr, optional: Tile identifier. Default is ‘T07’.

Returns

outdirstr: Path to the created or existing output directory.

BackPrep.default = Multiline-String

Show Value

"""
# Default configuration file for SWarp 2.38.0
# EB 2019-07-10
#
#----------------------------------- Output -----------------------------------
IMAGEOUT_NAME         foo.fits      # Output filename
WEIGHTOUT_NAME      foo.weight.fits # Output weight-map filename

HEADER_ONLY            N               # Only a header as an output file (Y/N)?
HEADER_SUFFIX          .head           # Filename extension for additional headers

#------------------------------- Input Weights --------------------------------

WEIGHT_TYPE            NONE            # BACKGROUND,MAP_RMS,MAP_VARIANCE
                                       # or MAP_WEIGHT
WEIGHT_SUFFIX          .weight.fits    # Suffix to use for weight-maps
WEIGHT_IMAGE                           # Weightmap filename if suffix not used
                                       # (all or for each weight-map)

#------------------------------- Co-addition ----------------------------------

COMBINE                Y               # Combine resampled images (Y/N)?
COMBINE_TYPE           MEDIAN          # MEDIAN,AVERAGE,MIN,MAX,WEIGHTED,CLIPPED
                                       # CHI-OLD,CHI-MODE,CHI-MEAN,SUM,
                                       # WEIGHTED_WEIGHT,MEDIAN_WEIGHT,
                                       # AND,NAND,OR or NOR

#-------------------------------- Astrometry ----------------------------------

CELESTIAL_TYPE         NATIVE          # NATIVE, PIXEL, EQUATORIAL,
                                       # GALACTIC,ECLIPTIC, or SUPERGALACTIC
PROJECTION_TYPE        TAN             # Any WCS projection code or NONE
PROJECTION_ERR         0.001           # Maximum projection error (in output
                                       # pixels), or 0 for no approximation
CENTER_TYPE            MANUAL          # MANUAL, ALL or MOST
CENTER                %.4f, %.4f       # Coordinates of the image center
PIXELSCALE_TYPE        MANUAL          # MANUAL,FIT,MIN,MAX or MEDIAN
PIXEL_SCALE            2            # Pixel scale
IMAGE_SIZE          2000,2000          # Image size (0 = AUTOMATIC)

#-------------------------------- Resampling ----------------------------------

RESAMPLE               Y               # Resample input images (Y/N)?
RESAMPLE_DIR           .               # Directory path for resampled images
RESAMPLE_SUFFIX        .resamp.fits    # filename extension for resampled images

RESAMPLING_TYPE        LANCZOS3        # NEAREST,BILINEAR,LANCZOS2,LANCZOS3
                                       # LANCZOS4 (1 per axis) or FLAGS
OVERSAMPLING           0               # Oversampling in each dimension
                                       # (0 = automatic)
INTERPOLATE            N               # Interpolate bad input pixels (Y/N)?
                                       # (all or for each image)

FSCALASTRO_TYPE        FIXED           # NONE,FIXED, or VARIABLE
FSCALE_KEYWORD         FLXSCALE        # FITS keyword for the multiplicative
                                       # factor applied to each input image
FSCALE_DEFAULT         1.0             # Default FSCALE value if not in header

GAIN_KEYWORD           GAIN            # FITS keyword for effect. gain (e-/ADU)
GAIN_DEFAULT           0.0             # Default gain if no FITS keyword found

#--------------------------- Background subtraction ---------------------------

SUBTRACT_BACK          N               # Subtraction sky background (Y/N)?
                                       # (all or for each image)

BACK_TYPE              AUTO            # AUTO or MANUAL
                                       # (all or for each image)
BACK_DEFAULT           0.0             # Default background value in MANUAL
                                       # (all or for each image)
BACK_SIZE             2048             # Background mesh size (pixels)
                                       # (all or for each image)
BACK_FILTERSIZE        3               # Background map filter range (meshes)
                                       # (all or for each image)

#------------------------------ Memory management -----------------------------

VMEM_DIR               .               # Directory path for swap files
VMEM_MAX               2047            # Maximum amount of virtual memory (MB)
MEM_MAX                256             # Maximum amount of usable RAM (MB)
COMBINE_BUFSIZE        256             # RAM dedicated to co-addition(MB)

#------------------------------ Miscellaneous ---------------------------------
DELETE_TMPFILES        Y               # Delete temporary resampled FITS files
                                       # (Y/N)?
COPY_KEYWORDS          OBJECT          # List of FITS keywords to propagate
                                       # from the input to the output headers
WRITE_FILEINFO         N               # Write information about each input
                                       # file in the output image header?
WRITE_XML              Y               # Write XML file (Y/N)?
XML_NAME               swarp.xml       # Filename for XML output
VERBOSE_TYPE           NORMAL          # QUIET,LOG,NORMAL, or FULL

NTHREADS               0               # Number of simultaneous threads for
                                       # the SMP version of SWarp
                                       # 0 = automatic
"""

BackPrep.exec_dir

BackPrep.prep_one_tile(field='LMC_c42', tile='T07', redo=False)

Prepare SWarp configuration and run script for one tile.

This function reads the summary file for a field/tile combination, creates the necessary output directories, generates a SWarp configuration file, and creates a run script with SWarp commands for each image.

Parameters

fieldstr, optional: Field name. Default is ‘LMC_c42’.
tilestr, optional: Tile identifier. Default is ‘T07’.
redobool, optional: If True, regenerate all background files even if they exist. If False (default), skip files that already exist.

Returns

nint: Number of background files that need to be created.

Raises

IOError: If the summary file or input directory cannot be found.

Notes

The function creates: - Output directory: SWARPDIR/field/tile/ - SWarp config: SWARPDIR/field/tile/swarp.default - Run script: SWARPDIR/field/tile/RunSwarp

The run script is made executable and contains one SWarp command per input image.

Examples

Prepare configuration for a single tile:

>>> n = prep_one_tile('LMC_c42', 'T07')
>>> print(f"{n} files need processing")

Force regeneration of all files:

>>> n = prep_one_tile('LMC_c42', 'T07', redo=True)

BackPrep.run_back(field='LMC_c42', tile='T07')

Execute SWarp for background field processing.

This function changes to the appropriate output directory and executes the RunSwarp script to generate background images using SWarp.

Parameters

fieldstr, optional: Field name. Default is ‘LMC_c42’.
tilestr, optional: Tile identifier. Default is ‘T07’.

Returns

None

Notes

The function: - Changes to the SWarp output directory - Executes the RunSwarp script - Captures output to Swarp.out.txt - Prints the last 10 lines of output - Reports total execution time - Returns to the original execution directory

The function filters out progress indicators from SWarp output to keep the log file clean.

Examples

Run SWarp for a single tile:

>>> run_back('LMC_c42', 'T07')
***BackPrep: Completely done for tile T07 in 123.4 s

BackPrep.steer(argv)

Parse command-line arguments and coordinate BackPrep operations.

This steering function processes command-line arguments and orchestrates the setup and execution of SWarp background processing for specified fields and tiles.

Parameters

argvlist of str: Command-line arguments including script name.

Returns

None

Notes

The function processes the following workflow:

Parse command-line arguments
Determine which tiles to process
Set up SWarp configuration for each tile
Optionally execute SWarp commands (if -run specified)
Log all operations to a field-specific log file

Global variables SWARPDIR and PREPDIR may be modified if -indir is used.

Examples

From command line:

$ python BackPrep.py -run LMC_c42 T07

From within Python:

>>> import sys
>>> steer(['BackPrep.py', '-run', 'LMC_c42', 'T07'])

BackPrep

Synopsis

Command Line Usage

Description

Version History

Examples

Version History

Examples

Attributes

Functions

Module Contents

Parameters

Returns

Parameters

Returns

Raises

Notes

Examples

Parameters

Returns

Notes

Examples

Parameters

Returns

Notes

Examples

See Also