The software package is composed at the moment of two Python scripts, one to simulate the data (simulate.py) and the other to compare simulations (compare.py). The usage of the programs is displayed by calling them with the option -h or --help.
The first step to simulate the effect of one source (usually an A-Team) on our observation is to create a mock measurement set (MS) with the information of the observation (using makems). Later the calibration tables of the observing modes have to be updated into the MS (using makebeamtables). Then it is possible to simulate using BBS the effect of a model source on the data. The commands and parsets needed for all those steps are generated with the command "simulate.py".
The second step is to check what is the effect of the source on the target field. This effect can be quantified in two ways. The first is to check the amplitude of the source on the target field. All the data points that present flux from the source above a certain threshold are considered as affected and the final percentage of the data affected is shown. The second way is to compare the flux of the interfering source with the flux of a central source in the target field (using a scaling factor called "level"). If the flux of the source is 'level' times higher than the flux of the central source in a data point this point is considered to be affected by the source.
The software depends on several Python modules that are already installed in the LOFAR clusters.
At the moment it can be found in the directory ~montes/xmm/simulation. It is a git repository so you could obtain a copy using: git clone ~montes/xmm/simulation but you do not need to do that in order to run the software.
To simulate an observation, the position, observation time, and length of the observation, of the target must be specified with the options --ra, --dec, --time and --n-time (in number of steps of 10 seconds) respectively. It is also interesting to specify the name of the field simulated using the option --name. The option --overwrite may be needed to allow the overwriting of parset and MS files. The sources to be simulated can be specified after the option --source. Currently, it is possible to specify CygA, CasA4, TauA, VirA4, HydraA. It is also possible to use CasA and VirA but the simulation can be very slow. The sources 3C53 and 3C237 are also included. The data are stored in /data/scratch/<user_name>/simulation/ by default but an alternative location can be specified with the option --path. Finally, the script generates by default the files for an HBA observation, if the option --lba is specified, an LBA observation is simulated.
With the current version of the program, the working directory and the necessary parsets are created but the commands are only displayed on screen and must be executed by the user.
Example
python ~montes/xmm/simulation/simulate.py --ra 10:47:00.0
--dec 58.05.00.0 --time 2013/03/03/19:00:00 --n-time 3600
--name Lockman_Hole_field --source CasA4 CygA TauA VirA4
--overwrite --lba
WARNING: The format used for "ra", "dec" and "time" is the same format that will be entered into the parset. Remember that the declination uses dots instead of colons.
TODO:
- Allow the direct execution of the commands by the script
- Allow different antenna configurations. At the moment, the default HBA configuration is HBA_DUAL_INNER and the default LBA configuration is LBA_OUTER.
- Test the option --skymodel
The effect of an A-team source can be assessed using this script. The simulation file (that created with simulate.py) of an A-Team source must be entered. The default threshold to consider that a source is affecting a data point is 5 Jy. A different threshold or set of threshold can be specified with the option -t or --threshold. The output is the median value of the percentage of data points affected with respect to the time for the XX and YY croscorrelations.
Example
python ~montes/xmm/simulation/compare.py
/data/scratch/montes/simulation/20130303_Lockman_Hole_field_LBA_CygA.MS
-t 2.5 5. 10. -f "median"
It is also possible to enter the simulated MS of the central source using the option -s or --source. If this is entered, the comparison levels can be specified with the option -l or --level. The percentages displayed are with respect to the points for which the flux of source is stronger than "level" times the flux of the central source.
Example
python ~montes/xmm/simulation/compare.py
/data/scratch/montes/simulation/COSMOS_20130219_sim_CygA.MS
-s/data/scratch/montes/simulation/COSMOS_20130219_sim_source.MS
-l 0.01 0.1 0.5 1. -f "median"
The options -l plus -s can be used together mixed with the options -t.
NOTE: Due to a bug in the Python module "argparse", if the options -t or -l are used, they can not be followed by the name of the A-Team source. They can be followed by any other option or, the name of the A-Team source can be placed at the beginning, just after compare.py.
TODO:
- Allow the simultaneous comparison of several A-Team sources.