Introduction to CASACrystal Brogan

ALMA CASA Subsystem Scientist (NRAO/NAASC)

With lots of help from Steve Myers (Project Scientist)

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CASA (Common Astronomy Software Applications)

CASA is the offline data reduction package for ALMA and EVLABeta Release Status:

in Beta Release since October 2007

Roughly biannual “patches”

register at http://my.nrao.edu

Current Release: Beta Release Patch 2.4Next Release @Nov ’09 (3.0)

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Outline

IPython & PythonCASA helpCASA task interfaceMS and data selectionThe Memory SticksDocumentation

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CASA InterfaceIPython

shell accessautoparenthesis (autocall)command historysession logging

ipython.log – ipython command historycasapy.log – casa messages

numbered input/outputhistory/searching

PythonCookbook Appendix D

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Python Pointersto run a .py script:

execfile(‘<scriptname>’)example: execfile(‘ngc5921_demo.py’)

indentation matters!be careful when doing cut-and-paste to Pythoncut a few (4-6) lines at a time

variables are global when using task interface!tasknames are objects (not variables)

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Tasks and tools in CASATasks - high-level functionality

function call or parameter handling interface

these are what you should use in tutorial

Tools - complete functionalitytool.method calls, used by tasks

sometimes shown in tutorial scripts

CASA Tutorial -- 7 October 2008

Key TasksTo see list of tasks after startup organized by type:

>tasklist

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Task Executiontwo ways to invoke:

call from Python as functions with argumentstaskname( arg1=val1, arg2=val2, ... )

unspecified parameters will be defaulted (globals not used)

use standard tasking interfaceuse global variables for task parameters

see Chapter 1.3 in Cookbook

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Task Interfacestandard tasking interface

use parameters set as global Python variablesset <param> = <value> (e.g. vis = ‘ngc5921.demo.ms’ )

parameter manipulation commandsusing inp , default , saveinputs , tget

execute<taskname> or go ( e.g. clean() )

return valuessome tasks return Python dictionaries, e.g. myval=imval()

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Task Interfaceexamine task parameters with inp :

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Expandable Parametersboldface parameter are expandable

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Parameter Checkingsanity checks of parameters in inp :

erroneousvalues in red

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Help on TasksIn-line help:

>help ‘clean’ OR >pdoc clean

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Tools in CASACASA Toolkit underneath tasks

core AIPS++ code (mostly in C++)

tools are functions call from casapy as <tool>.<method>()

default tool objects are pre-constructede.g. imager (im) , calibrater (cb), ms (ms) , etc. (see toolhelp)

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CASA Tool Listlist of default tools from toolhelp :

tools described in the CASA User Reference Manual:

http://casa.nrao.edu/docs/casaref/CasaRef.html

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The Measurement Setthe MS is a directory on disk

the MAIN table in table.* files

also contains sub-tablese.g. FIELD, SOURCE, ANTENNA, etc.

sub-tables are sub-directories

to copy must cp -rf to get contents

Best to remove ms with rmtables(‘filename’)WARNING: moving a MS can break cal-table dependencies

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Example MSExample: ls ngc5921.usecase.ms

ls ngc5921.usecase.ms/FIELD

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MAIN Table ContentsExample using task browsetable:

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Data Selection Examplestandard selection parameters

e.g. for task gaincal:

field and spw common standard selections

expandable selectdata with other selections as sub-parameters

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Data Selection Syntaxsee Chapter 2.5 of Cookbook

field - string with source name or field IDcan use ‘*’ as wildcard, first checks for name, then ID

example: field = ‘1331+305’ ; field = ‘3C*’ ; field = ‘0,1,4~5’

spw - string with specwindow ID plus channelsuse ‘:’ as separator of spw from optional channelization

use ‘^’ as separator of channels from step/width

example: spw = ‘0~2’ ; spw = ‘1:10~30’ ; spw = ‘2~5:5~54^5’

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Selection Syntaxsee Chapter 2.5 of Cookbook

antenna - string with antenna name or IDfirst check for name, then ID (beware VLA name 1-27, ID 0-26)

example: antenna = ‘1~5,11’ ; antenna = ‘VA*’

timerange - string with date/time rangespecify ‘T0~T1’ , missing parts of T1 default to T0, can give ‘T0+dT’

example: timerange = ‘2007/10/16/01:00:00~06:30:00’

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The Memory Sticks etc.Contents:

“Install_README” - installation instructions

“installation” - directory contains 32-bit linux and intel mac files. Please see me if you need 64-bit linux. Please install before Wed.

“casa_scripts_and_data.tar” copy this to your hard drive before Wed. Note a copy of the casa cookbook is included in this directory. A slightly newer version is available at http://www.aoc.nrao.edu/~smyers/naug/doc/cookbook/casa_cookbook.pdf

Additional CASA Scripts & Data Pagehttp://casa.nrao.edu/casatraining.shtml

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Getting User SupportFirst stop:

CASA Home: http://casa.nrao.edu

Cookbook, and “help” within CASA

CASA Helpdesk & Support“Helpdesk” at http://my.nrao.edu (will migrate to more user friendly helpdesk in future)

You will need to register first

Submit questions, suggestions, bugs

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CASA DocumentationCASA Analysis cookbook:

http://casa.nrao.edu/Doc/Cookbook/casa_cookbook.pdf

CASA User Reference Manual: • http://casa.nrao.edu/docs/casaref/CasaRef.html

• Python: • http://python.org/doc (e.g., see Tutorial for novices)

• IPython: • http://ipython.scipy.org/moin/Documentation

matplotlib: http://matplotlib.sourceforge.net/