saltprepare

Name

saltprepare – Prepare FITS files for PyRAF and IRAF reduction tasks

Usage

saltprepare images rawpath outimage outpref (clobber) logfile (verbose)

Parameters

images

String. List of FITS images to prepare. Data can be provided as a comma-separated list, or a string with a wildcard (e.g. ‘images=S20061210*.fits’), or a foreign file containing an ascii list of image filenames. For the ascii list option, the filename containing the list must be provided preceded by a ‘@’ character, e.g. 'images=@listoffiles.lis‘. The list can contain data files from multiple SALT instruments.

outimage

String. A list of images. Data can be provided as a comma-separated list, or a string with a wildcard (e.g. ‘outimages=rS20061210*.fits’), or a foreign file containing an ascii list of image filenames. For ascii list option, the filename containing the list must be provided preceded by a ‘@’ character, e.g. 'outimages=@listoffiles.lis‘. This list must be of the same size as the images argument list.

outpref

String. If the outpref string is non-zero in length and contains characters other than a blank space, it will override any value of the outimages argument. Output file names will use the name list provided in the images argument, but adding a prefix to the basename of each output file defined by outpref. An absolute or relative directory path can be included in the prefix, e.g. ‘outpref=/Volumes/data/p’.

(createvar)

Hidden boolean. If set to ‘yes’, the task will add on variance and bad pixel extensions to the data.

(badpixelimage)

Hidden string. If createvar is set to ‘yes’ and this file is not None, then saltprepare will use this file to add the badpixelmask. If badpixelimage is not set, then it will create the badpixelmask from the file itself.

(clobber)

Hidden boolean. If set to ‘yes’ files contained within the outpath directory will be overwritten by newly created files of the same name.

(logfile)

String. Name of an ascii file for storing log and error messages from the tool. The file may be new, or messages can also be appended to a pre-existing file.

(verbose)

Hidden Boolean. If verbose=n, log messages will be suppressed.

Description

SALTPREPARE prepares the SALT data for pipeline processing. The main purpose of this task is to verify the correct header key words and the data file format.

Saltprepare is currently a relatively trivial task that adds several missing but required keywords to the keyword headers of FITS data files. These keywords are not written to the file at the telescope but are required in order to improve efficiency in the data reduction pipeline and retain consistency with the IRAF-based tools.

The user may also select to create variance and bad pixel frames for the data by setting the createvar varialble. If selected, variance frames will be created based on the pixel variance and the readnoise. The user can also supply a bad pixel frame, but if one is not supplied, one can be created from the data itself assuming all pixels are good.

The following list describes each new keyword:

NSCIEXT (integer)

Primary HDU. The number of HDU in the file containing data images.

NEXTEND (integer)

Primary HDU. The number of HDU containing an image. The number will be greater than NSCIEXT if bad pixel and variance maps are added to the file for future statistical error propagation (not currently implemented).

SAL-TLM (string)

Primary HDU. The time and date that the file was last altered by a SALT task.

PPREPARE or SPREPARE (string)

Primary HDU. The time and date that the file was processed by the saltprepare task. The ‘P’ and ‘S’ prefix refers to whether the data was recorded by RSS (PFIS) or SALTICAM. The difference is retained for back-compatibility with the SALT IRAF tools that make a distinction between the two instruments.

EXTNAME (string)

Image HDUs. The Name of the HDU. All science images are given the name ‘SCI’. Bad pixel and variance maps will be given alternative names, to be decided upon.

EXTVER (integer)

Image HDUs. The HDU number which refers to the order of the image in the sequence of FITS extensions.

Examples

1. To prepare raw FITS files residing in the /Volumes/data1/ and create new files with paths and names stored in the ascii list outimages.lis:

--> saltprepare images='P*.fits'
outimages='@outimages.lis' outpref='' logfile='salt.log'

2. To prepare raw FITS files residing in the /Volumes/data1/ and create new files in the directory /Volumes/data2 with prefix ‘p’, over-write existing files, create variance frames and badpixelmasks, and suppress log messages:

--> saltprepare images='/Volumes/data2/P*.fits'
outimages='' outpref='/Volumes/data2/p'
createvar='yes', badpixelmask='bpm.fits'
clobber='yes' logfile='salt.log' verbose='no'

Time and disk requirements

Individual unbinned raw full-frame RSS files can be 112MB in size. It is recommended to use workstations with a minimum of 512MB RAM. On a linux machine with 2.8 Ghz processor and 2 Gb of RAM, one 2051x2051 image in 0.15 sec.

Bugs and limitations

Currently there is no statistical error propagation in the SALT pipeline tasks. However, saltprepare can create multiple new image extensions containing a) bad pixel maps and b) varaiance maps for all amplifiers.

Send feedback and bug reports to salthelp@saao.ac.za

See also

saltpipe saltclean