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Preparing fitsidi data

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Jack Radcliffe edited this page Jul 6, 2022 · 4 revisions

Preparing fitsidi data - EVN/LBA only (prepare_data)

The prepare_data step is used only for data from the European VLBI Network (EVN) and Long Baseline Array (LBA) whose observatory products need to be appended to the FITS-IDI files. These steps use the tools developed by Mark Kettenis (https://github.com/jive-vlbi/casa-vlbi) but have now been fully parallelised. The relevant parameters for this step in the params files are:

Parameters

    "prepare_data":{
        "antab_file"        :  "auto",
        "flag_file"         :  "auto",
        "gaincurve":{
            "min_elevation" :   0.0,
            "max_elevation" :  90.0
        },
        "hpc_options":{
            "partition"     :  "default",
            "walltime"      :  "default",
            "nodes"         :    -1,
            "cpus"          :    -1,
            "mpiprocs"      :    -1,
            "nodetype"      :  "default"
        }
    },

The antab_file and flag_file contain the information on system temperatures/ gain curves and the observatory made flags, respectively. The system temperatures will appended to copy of the fitsidifiles (which are specified by the fitsidi_path and fitsidi_files) into the current working directory. You may need to generate your own antab files for Global and LBA data (see the antab file section). These need to include both the gaincurve and system temperature information!

Setting antab_file or flag_file to "auto" will cause the code to search for the correct antab/flag files for the project. The code therefore searches for files matching <project_code>.antab or <project_code>.uvflg where you replace <project_code> with the project code. This is the typical naming of files used by the EVN. The code will also find the tables matching to different correlator passes e.g., <project_code>_1.antab.

The gaincurve elevation parameters are normally ok set as default, but you may want to adjust for observations at low elevation.

Antab files

A typical antab file will include both information on the gaincurves of the telescopes and the system temperatures. For LBA and global VLBI, you will need to generate these by yourself and combine into a single antab file for this pipeline to work properly. An example antab format for the project EG078B and telescope Sheshan is given below. Please contact the observatory with regards to making these.

GAIN SH  ELEV DPFU=0.074669,0.076471       FREQ=1200,3400
POLY=5.0085E-01,2.2805E-02,-2.6048E-04
/
TSYS SH FT=1.0 TIMEOFF=0
INDEX= 'R1', 'R2', 'L1', 'L2', 'R3', 'R4', 'L3', 'L4', 'R5', 'R6', 'L5', 'L6', 'R7', 'R8', 'L7', 'L8'
/
156 07:59.83  36.9  34.2  32.5  26.2  37.8  39.6  37.7  38.8  39.9  48.2  40.0  46.5  44.9  78.6  45.7  72.4 
156 08:00.00  42.3  36.8  35.9  30.6  39.7  42.8  41.2  42.3  41.9  50.1  40.8  48.4  44.9  70.6  45.7  76.0 
156 08:00.25  36.9  32.7  32.5  26.1  36.7  39.6  37.2  38.8  39.9  48.2  40.0  46.5  44.0  68.2  45.7  82.4 
156 08:00.50  36.9  33.5  32.5  26.1  36.7  39.6  37.1  38.8  39.9  47.3  40.0  46.5  44.0  70.6  45.7  81.0 
156 08:00.75  36.9  36.8  32.5  26.1  36.7  39.6  37.1  38.8  39.9  48.2  40.0  46.5  44.0  65.8  45.7  71.4 
156 08:01.00  37.8  32.7  32.8  28.1  36.7  39.6  37.1  38.8  39.9  47.3  40.0  46.5  44.0  57.8  45.7  66.2

Expected inputs

  • Fitsidifiles in the fitsidi_path folder
  • <project_code>.antab (in the cwd)
  • <project_code>.uvflg (in the cwd if available)

Expected outputs

  • Fitsidifiles in the current working directory with Tsys information appended
  • <project_code>.gc - table including gaincurve information from Tsys
  • <project_code>_casa.flags - text file including information on observatory flags
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