Introduction to CASA

1
Introduction to CASA

• ( originally prepared by J. McMullin)

2
CASA

• Common Astronomy Software Applications
• Post processing of radio astronomical data (ALMA,
  EVLA projects)
• C application libraries with Python interface
  (iPython)
• Currently Beta release (Oct 15, 2007, patch 0.5
  on Nov 15,2007)
• Patch 1.0 will be Feb 15, 2008

3
CASA Web

• http//casa.nrao.edu -- CASA Home Page
• Main resource for end users
• http//my.nrao.edu -- NRAO Services (incl.
  registration/download of CASA)
• Help Desk/Installation Front manned by
  scientists (ALMA, ARC, NAUG, etc) to handle
  front-line user support.

4
CASA Development

• CASA management
• Manager (TBD) interim,Brian Glendenning
• Steve Myers, Project Scientist

• CASA developers (current)
• Sanjay Bhatnagar
• David King
• Shannon Jaeger (Univ. Calgary)
• Kumar Golap
• George Moellenbrock
• Raymond Rusk (DRAO)
• Darrell Schiebel
• Tak Tsutsumi
• Boyd Waters
• Honglin Ye
• Wes Young
• (Michel Caillat, Laura Glendenning)

5
CASA Documentation

• CASA Analysis cookbook http//casa.nrao.edu/Doc/C
  ookbook/casa_cookbook.pdf
• CASA User Reference Manual http//casa.nrao.edu/d
  ocs/casaref/CasaRef.html
• Python http//python.org/doc (e.g., see Tutorial
  for novices)
• IPython http//ipython.scipy.org/moin/Documentati
  on
• matplotlib http//matplotlib.sourceforge.net/

6
CASA Installation

• Currently requires root permission (for Linux
  flavors)
• (Experimental) non-root version is also available
  now
• Download from my.nrao.edu after registration
• Supports
• Fedora Core 6, Fedora 7
• RH Linux 4, 5
• Mac OSX Intel
• RH Linux 4, ACS 6.0.4

7
CASA Interface

• IPython
• Python
• CASA help
• CASA task interface

8
CASA Interface

• IPython
• shell access
• autoparenthesis (autocall)
• command history
• macro
• session logging (ipython.log, casapy.log)
• numbered input/output
• history/searching

9
Python Pointers

• to run a .py script
• execfile(ltscriptnamegt)
• example execfile(ngc5921_usecase.py)
• indentation matters!
• be careful when doing cut-and-past to Python
• variables are global!
• tasknames are objects (not variables)

10
CASA Interface

• CASA help
• startup
• tasklist
• taskhelp
• toolhelp
• help taskname
• help par.par_name

• CASA Task Interface
• globals
• error handling
• inp command
• task execution
• default
• saveinputs/tget
• Logging GUI

11
Tasks in CASA

• tasks high (user) level functionality
• call from Python as functions
• standard tasking interface
• parameter manipulation using inp , default ,
  saveinputs , tget
• arguments are parameters
• these are global Python variables ( set ltparamgt
  ltvaluegt )
• see Chapter 1.3 in Cookbook

12
Task Interface

• examine task parameters with inp

13
Expandable Parameters

• boldface parameter are expandable

14
Parameter Checking

• sanity checks of parameters in inp

15
Help on Tasks

• In-line help lttasknamegt command

16
Tools in CASA

• CASA Toolkit underneath tasks
• core AIPS code (mostly in C)
• tools are functions
• call from casapy as lttoolgt.ltmethodgt()
• default tool objects are pre-constructed
• e.g. imager (im) , calibrater (cb), ms (ms) ,
  etc. (see toolhelp)

17
Tool Objects

• tools run as distributed objects (DO)
• default DOs are pre-constructed
• these are used by the tasks
• one for each tool
• are persistent
• DANGER! tasks can trample on each other

18
Help on Tools

• use ltTABgt completion in casapy to list
• also help lttoolgt.ltmethodgt or lttoolgt.ltmethodgt?

19
Asynchronous Tasks

• run tasks in background
• set parameter asyncTrue
• runs as separate process
• use taskmanager tool (tm) to monitor (Cookbook
  Chapter 1.3.2)
• messages will appear in logger in the
  asynchronous order
• will instantiate separate tools
• useful to avoid known problems (e.g. exportfits /
  importfits)

20
Functionality Census

• Import VLA archive, UVFITS, image FITS
• Export UVFITS, image FITS
• Information listcal, listhistory, listobs,
  imhead
• Editing flagautocorr, flagdata, flagmanager,
  plotxy, viewer
• Display clearplot, plotants, plotcal, plotxy,
  viewer
• Calibration accum, applycal, bandpass, gaincal,
  fluxscale, clearcal, listcal, smoothcal
• Imaging clean, feather, ft, invert, makemask,
  mosaic
• Modelling setjy, uvcontsub, uvmodelfit

21
Toolkit Census

• cb - calibration
• cp - calibration solution plotting
• fg - flagging, flag management
• ia - image analysis
• im - imaging
• me - measures

• mp - MS plot (e.g., data vs quantities)
• ms - MS utilities
• qa - quanta
• sm - simulation
• tb - table access
• tp - table plotting

22
Test data available in the data repository
(https//svn.cv.nrao.edu/svn/casa-data/trunk/regr
essions/)

• ATST1
• NGC5921, NGC7538, G192 (VLA SF)
• GGTAU, L02D, H121 (PdBI SF)
• ATST2
• NGC1333 (VLA), NGC4826 (BIMA)
• ATST3
• NGC4826 (BIMAKP 12m)
• Orion (VLAGBT)
• ATST4
• B0319 (Flux cal for NGC1333)
• ATST5
• FLS3, IRC10216, OrionS (GBT SD)

23
Demo

• Installation
• Go to http//my.nrao.edu
• Assess the build
• Download sample data set
• svn co https//svn.cv.nrao.edu/svn/casa-data/trunk
  /regression/ATST1/NGC921
• Start up
• Type casapy
• Execute test regression script
• os.system(cp sys.path2/ngc5921_regression.p
  y .)
• execfile ngc5921_regression.py
• Illustrate interface features
• CASAdemoscript.py