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Basic Information on atlod
Task: atlod
Purpose: Convert an RPFITS file into Miriad uv format.
Categories: data transfer
ATLOD is a MIRIAD task, which converts a uv data-set from the RPFITS
format to Miriad format.
Key: in
Name of the input RPFITS files. Several names can be given -- wildcard
expansion is supported. If a single name is given, this can be a raw
tape device name (e.g. /dev/nrst0 in UNIX) containing several files.
In this case, see the NFILES keyword below. There is no default.
Key: out
Name of the output Miriad uv data-set. No default.
Key: ifsel
IF number to select. Default is all IFs. For example,
if you observed with 5 GHz (frequency 1) and 8 GHz (frequency 2)
simultaneously, IF 1 would be the 5 GHz data and IF 2 would
be the 8 GHz data.
Key: restfreq
The rest frequency, in GHz, for line observations. By default,
the value in the RPFITS file is used. Giving a value for the
"restfreq" parameter overrides the RPFITS file value. If you
do set this parameter, you MUST give the same number of values as the
number of IFs written out. A value of 0 is used for a continuum
observation. For example, if you have two IFs, the first of
which is HI, and the second is continuum, use
restfreq=1.420405752,0
Key: options
This gives extra processing options. Several can be given,
separated by comas.
'birdie' For CABB data:
CABB generates self-interference in a number of channels
across the spectrum due to 640 MHz clock harmonics.
These birdies are fixed in channel number for each CABB
configuration. The birdie option currently knows about
the 2048x1MHz continuum mode and flags the affected
channels, 100 band edge channels on each side, and, at
20 and 13cm, the unusable parts of the spectrum.
For pre-CABB data:
ATCA self-interference can corrupt channels at integral
multiples of 128 MHz. The birdie option flags these
channels. Additionally, in continuum (33 channels/128MHz)
mode, the birdie option dicards every second channel, plus
some edge channels. The channels discarded
are those most likely affected by the self-interference.
Discarding these channels does not have a
sensitivity penalty, because the effective channel
bandwidth is twice the channel separation.
'reweight' For pre-CABB data: re-weight the lag spectrum to
eliminate the "Gibbs" phenomena in continuum data
(33 ch/128 MHz); ignored for all other data.
'compress' Write output data in compressed format.
'noauto' Discard autocorrelation data. The default is to
copy the autocorrelation data.
'nocross' Discard cross-correlation data. The default is to
copy the cross correlation data.
'relax' Do not flag visibilities based on SYSCAL information.
The default is to flag visibilities if they have
not been preceded by a valid SYSCAL record, or if the
the values in the SYSCAL record look bad. SYSCAL
values are checked for sampler statistics being within
3% of 17.3%, or 0.5% of 50.0%, that the XY phase
is within 10 degrees of its running median, and that
the XY amplitudes are within 1 Jy or 10% of its running
median. The tests for xy phase and amplitude are
skipped for 3mm data (as there is no noise calibration
signal).
'mmrelax' This option is ignored, and is present for historical
reasons.
'unflag' Save any data that is flagged. By default ATLOD
discards most data that is flagged.
'opcorr' Correct for atmospheric opacity. This option is possible
for data measured after October 2003. Because of the way
system temperature is measured at 3mm (an "above atmosphere"
measurement), it is not appropriate for 3mm data. This option
is silently ignored for 3mm data. Generally it is only relevant for
7mm and 12mm observations. It does no harm (and negligible
good) for longer wavelengths.
'samcorr' Correct the pre-Dec93 data for incorrect sampler
statistics. Since December 1993, sampler corrections
are performed online. This option is silently ignored for
data measured after December 1993.
'xycorr' Apply the on-line measurements of the XY phase. This option
is silently ignored for 3mm data measured before October 2007.
'hanning' Hanning smooth spectra and drop every other channel
This option is ignored for 128-MHz, 33-channel data.
'bary' Use the barycentre as the velocity rest frame. The
default is to use the LSR frame.
'noif' Do not map the simultaneous IFs to the IF axis.
By default ATLOD attempts to map the simultaneous
frequencies to the IF axis. This will not be possible
if there are a different number of polarisations in
the different IFs.
'nopflag' If at least one polarisation of a set of 2 or 4 polarimetric
spectra are bad, ATLOD normally flags all of the
polarisations. Option nopflag changes this so that only
the nominally bad spectrum is flagged.
'hires' Treat bin data as measurements in the high time resolution
mode. The output dataset contains no bins, but instead
appears as data measured with small cycle times.
'pmps' Undo `poor man's phase switching'. This is an obscure option
that you should not generally use.
'single' Assume input is a single dish RPFITS file (from Mopra or
Parkes). This is usually used together with option 'relax'.
'caldata' Save visibilities associated with certain system
calibrations. Currently this consists of reference pointing
calibration and "paddle" measurements.
'nocacal' Flag data that atlod suspects is taken during a CACAL scan.
There is potential for error in atlod determining which data
are and are not part of a cacal scan. Use this with caution.
'nopol' Discard data that is not "parallel hand" Stokes type.
'rfiflag' Flag channels at frequencies that are known to be bad
This uses the file rfiflag.txt in the current directory or
the default version in MIRCAT. The file should contain
2 frequencies per line, the lower and upper end of the
rfi in MHz. Precede comments with a '#'.
Key: nfiles
This gives one or two numbers, being the number of files to skip,
followed by the number of files to process. This is only
useful when the input is a tape device containing multiple files.
The default is 0,1 (i.e. skip none, process 1 file).
NOTE: Using this feature to skip many files on a tape is VERY
inefficient. It is far faster to skip using operating system commands.
When doing this, however, you should be aware is that every RPFITS files
consists of 3 tape files. Thus you will want to skip three times as
many tape files as RPFITS files. For example, in UNIX, to skip 10
RPFITS files, use
mt -f /dev/nrst0 fsf 30
Key: nscans
This gives one or two numbers, being the number of scans to skip,
followed by the number of scans to process. NOTE: This applies to
all files read. The default is to skip none and process all scans.