ATLOD: Reading RPFITS Files

ATCA data will be initially in RPFITS format. This needs to be converted to Miriad's format, by task atlod, before any further processing can be done. We will discuss the various input parameters to Miriad atlod.

Typical inputs for atlod are given below.

in=/dev/nrst0 Input is either exabyte name
in=92-06-10_2110.C159 or RPFIT file.
out=0823.uv Output visibility data set.
options=birdie,reweight,xycorr Normal continuum mode options, or
options=birdie,hanning,compress possible spectral line options.
nfiles=0,3 Skip 0, then read 3 files.
nscans Unset to save all scans

Miriad's atlod saves a number of on-line measurements as visibility variables. These measurements may by helpful in analysing and flagging the data. They can be plotted and listed with task varplt (see Section 10.6). These on-line parameter, and its Miriad variable name, are described below.

This is the on-line measurement of the XY phase. It is important to examine this measurement if you are doing polarimetry.

This is the amplitude of the correlation between the X and Y polarization channel of a given antenna.

xsampler, ysampler:
These variables give the sampler statistics for the
MMX and Y polarization channels. There are three numbers per antenna per IF, which reflect the sampler levels. They should have values of 17.3, 50 and 17.3. Thus for six antennas, the xsampler variable will consist of 18 numbers per IF.

xtsys, ytsys:
These give the system temperature, in Kelvin, for the X and Y polarization channels. Unfortunately Miriad tasks were originally developed around a single polarization model of a telescope, and so most tasks that concern themselves with system temperature do not handle dual polarization systems. The partial workaround used in Miriad has been to store the geometric mean of the X and Y system temperatures in the variable systemp. It is this variable that Miriad tasks use when they need to use the system temperature value.

axisrms, axismax:
These give the antenna rms and maximum tracking errors in a particular cycle. The units are arcseconds.

These give various meterological measurements at the observatory as a function of time.

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