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Basic Information on atxy
Task: atxy
Purpose: Apply on-line XY phase measurements to Miriad data.
Categories: uv analysis
ATXY corrects data for XY phase errors. It determines the XY phase
measurements, either from the xyphase visibility variable or from
the text file written by AIPS ATLOD, averages them, and then
applies them to the data. The averaging step consists of finding
the median XY phase in a given interval.
Key: vis
The names of the input uv data sets. No default.
Key: xyphase
If the data were loaded with Miriad ATLOD, then they should contain
the on-line XY phase measurements in the xyphase variable. Howver
if the data were loaded with AIPS (and then transferred to Miriad
via FITS files), then you must give the name of the XY phase
text file written by AIPS. Generally it will be XYPHS_xx, where
xx is an AIPS user number.
Key: refant
Antennas to apply XY phase corrections to. Generally it is best to
apply corrections to only a single antenna -- the antenna which you
have the greatest confidence in the XY phase measurements. Often
this antenna will be the reference antenna during the observation.
If you apply the XY phase to a subset of antennas, one of these
antennas should be used as the ``refant'' antenna to GPCAL.
No default.
Key: interval
This gives the length of an averaging interval, in minutes. The
default is 30 minutes, but larger values may be useful.
Key: break
The times, in the normal Miriad format, where there are
break points. A ``break point'' gives a time where some form of
instrumental glitch took place, and the xyphases jumped. By
giving a break point, you prevent a solution interval from spanning
this time.
Key: sideband
Sideband indicators. If the input was loaded with AIPS ATLOD, and
if you averaged it into a channel-0 data-set, you must give the
sideband indicator (+1 or -1) for each IF. This information is needed
to convert between the AIPS and Miriad XY phase convention.
If the input is still multi-channel data, or you used Miriad ATLOD,
it is wiser to let this parameter default. Note that ATXY cannot
cope with channel-0 data-sets when the sideband indicators
change with time.
Key: out
The name of the output uv data set. No default.
Key: options
Extra processing options. Several options can be given,
separated by commas. Minimum match is supported. Possible values
are:
srcbreak Generate break points every time there is a change
in source.
undo Apply the negative of the XY phase correction. There
should be no sensible reason to ever use this option.
reweight Reweight the data (in the lag domain) to minimise the
so-called Gibbs phenomena and to help localise
interference.