imager_awimager

*Master Side of the recipe *

class lofarpipe.recipes.master.imager_awimager.imager_awimager

Master script for the awimager. Collects arguments from command line and pipeline inputs.

1. Load mapfiles and validate these
2. Run the awimage node scripts
3. Retrieve output. Construct output map file succesfull runs

Details regarding the implementation of the imaging step can be found in the node recipe CommandLine Arguments

A mapfile containing (node, datafile) pairs. The measurements set use as input for awimager executable

Recipe inputs

Parameters:

• executable – (ExecField) The full path to the awimager executable (ExecField)
• mapfile – (StringField) Full path for output mapfile. A list of thesuccessfully generated images will be written here (StringField)
• mask_patch_size – (FloatField) Scale factor for patches in the awimager mask (FloatField)
• output_image – (StringField) Path of the image to be create by the awimager (StringField)
• parset – (FileField) The full path to a awimager configuration parset. (FileField)
• sourcedb_path – (StringField) Full path of sourcedb used to create a mask for known sources (StringField)
• working_directory – (StringField) Working directory used on output nodes. Results location (StringField)

Recipe outputs (job.results[parameter])

Parameters:mapfile – (StringField) (StringField)

go()

This member contains all the functionality of the imager_awimager. Functionality is all located at the node side of the script.

*Node Side of the recipe*

class lofarpipe.recipes.nodes.imager_awimager.imager_awimager(job_id, host, port)

run(executable, environment, parset, working_directory, output_image, concatenated_measurement_set, sourcedb_path, mask_patch_size)

Parameters:

• executable – Path to awimager executable
• environment – environment for catch_segfaults (executable runner)
• parset – parameters for the awimager,
• working_directory – directory the place temporary files
• output_image – location and filesname to story the output images the multiple images are appended with type extentions
• concatenated_measurement_set – Input measurement set
• sourcedb_path – Path the the sourcedb used to create the image mask
• mask_patch_size – Scaling of the patch around the source in the mask

Return type:

self.outputs[“image”] The path to the output image

_calc_par_from_measurement(measurement_set, parset)

(1) calculate and format some parameters that are determined runtime. Based on values in the measurementset and input parameter (set):

1. <string> The cellsize
2. <int> The npixels in a each of the two dimension of the image
3. <string> The largest baseline in the ms smaller then the maxbaseline
4. <string> The number of projection planes

The calculation of these parameters is done in three steps:

1. Calculate intermediate results based on the ms.
2. The calculation of the actual target values using intermediate result
3. Scaling of cellsize and npix to allow for user input of the npix

_create_mask(npix, cell_size, output_image, concatenated_measurement_set, executable, working_directory, log4_cplus_name, sourcedb_path, mask_patch_size, image_path_directory)

(3) create a casa image containing an mask blocking out the sources in the provided sourcedb.

It expects:

1. the ms for which the mask will be created, it is used to de termine some image details: (eg. pointing)
2. parameters for running within the catchsegfault framework
3. and the size of the mask_pach. To create a mask, first a empty measurement set is created using awimager: ready to be filled with mask data

This function is a wrapper around some functionality written by: fdg@mpa-garching.mpg.de

steps: 1. Create a parset with image paramters used by: 2. awimager run. Creating an empty casa image. 3. Fill the casa image with mask data

_msss_mask(mask_file_path, sourcedb_path, mask_patch_size=1.0)

Fill casa image with a mask based on skymodel(sourcedb) Bugs: fdg@mpa-garching.mpg.de

pipeline implementation klijn@astron.nl version 0.32

Edited by JDS, 2012-03-16:

• Properly convert maj/minor axes to half length
• Handle empty fields in sky model by setting them to 0
• Fix off-by-one error at mask boundary

FIXED BUG

• if a source is outside the mask, the script ignores it
• if a source is on the border, the script draws only the inner part
• can handle skymodels with different headers

KNOWN BUG

• not works with single line skymodels, workaround: add a fake source outside the field
• mask patched display large amounts of aliasing. A possible sollution would be normalizing to pixel centre. ( int(normalize_x * npix) / npix + (0.5 /npix)) ideally the patch would increment in pixel radiuses

Version 0.3 (Wouter Klijn, klijn@astron.nl)

• Usage of sourcedb instead of txt document as ‘source’ of sources This allows input from different source sources

Version 0.31 (Wouter Klijn, klijn@astron.nl)

• Adaptable patch size (patch size needs specification)
• Patch size and geometry is broken: needs some astronomer magic to fix it, problem with afine transformation prol.

Version 0.32 (Wouter Klijn, klijn@astron.nl)

• Renaming of variable names to python convention