Importing Data from MIRIAD

A filler routine is currently being developed to convert native MIRIAD format data into a CASA measurement set, but it has not yet been completed. The following steps describe how to use FITS format files to transfer CARMA data into CASA, and should still be useful even after the filler is operational. At that time, a description of how to use the CARMA filler routine will be added to this page.

This page assumes you have MIRIAD already installed. All MIRIAD commands are given in their shell-script (csh) form, assuming that a number of variables have been defined at the top of your script.

For this example, the following items would be defined at the beginning of the csh shell script:

# in csh script

#!/bin/csh
# FILE = name of original MIRIAD-format file
set FILE="../c0437.1E_115NGC694.1.miriad"
# PROJECT = base file name for processed data files
set PROJECT="c0437"
# ANTPOS = the location of the file which contains updates to the CARMA antenna positions
set ANTPOS="../antpos.090613"

Preparing MIRIAD data for export to FITS

To minimize the data you are transferring over, select only the astronomically useful data:

# in csh script
uvcat vis=$FILE  select='-source(NOISE),-auto' out=$PROJECT.vis

If you need to apply an update for the antenna positions, or linelength corrections, you should do these before exporting to FITS.

To update antenna positions:

# in csh script
uvedit vis=$PROJECT.vis out=$PROJECT.ant apfile=$ANTPOS

To apply linelength corrections:

# in csh script
linecal vis=$PROJECT.ant
uvcat vis=$PROJECT.ant out=$PROJECT.lc

Currently, MIRIAD writes out the identity of the array as identified by Antenna 1, which is a formerly-OVRO antenna. Thus, without correction, the dataset will identify the array as OVRO rather than CARMA, which means that CASA will make the same mistake. To fix this problem, simply do a small header edit:

# in csh script
puthd in=$PROJECT.lc/telescop value=CARMA

Writing out the FITS files

Now you should be ready to write out your CARMA UV data. You will need to write out each spectral window as a separate FITS file, and then concatenate them back together within CASA. In your shell script, just use a "foreach" loop.

In this example, I am writing out the upper sideband windows only (windows 4,5, and 6):

2. Write out windows of individual sidebands to export to CASA for
3. testing--all sources in same file for common window

# in csh script
foreach i (4 5 6)
    fits in=$PROJECT.lc op=uvout select="win($i)" out="./fits/$PROJECT.$i.fits"
end

Constructing the CASA Measurement Set (MS)

--Mthornle 19:05, 23 November 2009 (UTC)