AIPS HELP file for RFI in 31DEC24
As of Fri Apr 26 20:40:16 2024
RFI: Look for RFI in a uv data set.
INPUTS
INNAME Input UV data
INCLASS Input UV data (class)
INSEQ Input UV data (seq. #)
INDISK Input UV data disk drive #
SOURCES Source (pointings) list
QUAL -10.0 Source qualifier -1=>all
CALCODE Calibrator code ' '=>all
TIMERANG Time range to process.
SELBAND Bandwidth to select (kHz)
SELFREQ Frequency to select (MHz)
FREQID Freq. ID to select.
BIF 0.0 100.0 Lowest IF number 0=>all
EIF 0.0 100.0 Highest IF number 0=>all
BCHAN 0.0 2048.0 Lowest channel number 0=>all
ECHAN 0.0 2048.0 Highest channel number 0=>all
SUBARRAY 0.0 1000.0 Subarray, 0=>all
DOCALIB -1.0 101.0 > 0 calibrate data & weights
> 99 do NOT calibrate weights
GAINUSE CL/SN table to apply
DOPOL -1.0 10.0 If >0 correct polarization.
PDVER PD table to apply (DOPOL>0)
BLVER BL table to apply.
FLAGVER Flag table version
DOBAND -1.0 10.0 If >0 apply bandpass cal.
Method used depends on value
of DOBAND (see HELP file).
BPVER Bandpass table version
SMOOTH Smoothing function. See
HELP SMOOTH for details.
UVRANGE 0. Min & max baseline (klambda)
SOLINT Time interval (sec)
BPARM (1) Fraction allowable bad
baselines.
(2) rms cutoff (Jy)
(3) Amp. factor for cutoff
DOCRT -1.0 132.0 > 0 -> use the terminal,
else use the line printer
> 72 => terminal width
OUTPRINT
Printer disk file to save
BADDISK -1.0 1000.0 Disks to avoid for scratch.
HELP SECTION
RFI
Type: Task
Use: Detect interference using the rms amplitude in each
correlator. Currently works for up to 8 correlators.
Either single or multisource data files can be processed.
This task computes the rms sine and cosine fluctuations in
each baseline/correlator and compares them with the value of
BPARM(2) plus the average source amplitude times BPARM(3), in
quadrature. If the fraction of bad baselines in any correlator
exceeds BPARM(1) a message is generated.
When a message is generated, the source name and time range
is given followed by a list of logical flags, one per correlator
in the order that they appear in the data. T indicates that the
corresponding correlator exceeded the maximum number of flagged
baselines; F indicates otherwise. If the output format is
sufficiently wide, the correlator number and the average rms
value of offending baselines for the worst baseline/correlation
is given.
Adverbs:
INNAME.....Input UV data file
INCLASS....Input UV data file (class). Standard defaults.
INSEQ......Input UV data file (seq. #). 0 => highest.
INDISK.....Input UV data file disk drive #. 0 => any.
SOURCES....List of sources (pointings) to be processed.
'*' or blank = all; a "-" before a source name
means all except ANY source named.
QUAL.......Only sources with a source qualifier number in the
SU table matching QUAL will be used if QUAL is not
-1.
CALCODE...."sources" may be selected on the basis of the
calibrator code given in the SU table.
' ' => any calibrator code selected
'* ' => any non blank code (cal. only)
'-CAL' => blank codes only (no calibrators)
NB: The CALCODE test is applied in addition to the
other tests, i.e. SOURCES and TIMERANG, in the
selection of sources to process.
CALCODE affects only the selection of calibrators.
TIMERANG...Time range of the data to be processed. In order:
Start day, hour, min. sec,
end day, hour, min. sec. Days relative to ref.
date.
SELBAND....Bandwidth of data to be selected. If more than
one IF is present SELBAND is the width of the
first IF required. Units = kHz. For data which
contain multiple bandwidths/frequencies the task
will insist that some form of selection be made
by frequency or bandwidth.
SELFREQ....Frequency of data to be selected. If more than
one IF is present SELFREQ is the frequency of the
first IF required. Units = MHz.
FREQID.....Frequency identifier to select (you may determine
which is applicable from the OPTYPE='SCAN' listing
produced by LISTR). If either SELBAND or SELFREQ
are set, their values overide that of FREQID.
However, setting SELBAND and SELFREQ may result in
an ambiguity. In that case, the task will request
that you use FREQID.
DOCALIB....If true (>0), calibrate the data using information in the
specified Cal (CL) table for multi-source or SN table for
single-source data. Also calibrate the weights unless
DOCALIB > 99 (use this for old non-physical weights).
BIF........First IF to select. 0=>all.
EIF........Highest IF to select. 0=>all higher than BIF
BCHAN......First channel to select. 0=>all.
ECHAN......Highest channel to select.
Use BIF, EIF, BCHAN, ECHAN to limit the total number of
correlators to 8 or fewer.
SUBARRAY...Subarray number to consider. 0=>all.
GAINUSE....CL table version number to apply. 0=> highest.
DOPOL......If > 0.5 then correct data for instrumental polarization
as represented in the AN or PD table. This correction is
only useful if PCAL has been run or feed polarization
parameters have been otherwise obtained. See HELP DOPOL
for available correction modes: 1 is normal, 2 and 3 are
for VLBI. 1-3 use a PD table if available; 6, 7, 8 are
the same but use the AN (continuum solution) even if a PD
table is present.
PDVER......PD table to apply if PCAL was run with SPECTRAL true and
0 < DOPOL < 6. <= 0 => highest.
BLVER......Version number of the baseline based calibration
(BL) table to appply. <0 => apply no BL table,
0 => highest.
FLAGVER....Specifies the version of the flagging table to be
applied. 0 => highest numbered table. <0 => no flagging
to be applied.
DOBAND.....If true (>0) then correct the data for the shape of the
antenna bandpasses using the BP table specified by BPVER.
The correction has five modes:
(a) if DOBAND=1 all entries for an antenna in the table
are averaged together before correcting the data.
(b) if DOBAND=2 the entry nearest in time (including
solution weights) is used to correct the data.
(c) if DOBAND=3 the table entries are interpolated in
time (using solution weights) and the data are then
corrected.
(d) if DOBAND=4 the entry nearest in time (ignoring
solution weights) is used to correct the data.
(e) if DOBAND=5 the table entries are interpolated in
time (ignoring solution weights) and the data are then
corrected.
BPVER......Specifies the version of the BP table to be applied
SMOOTH.....Specifies the type of spectral smoothing to be applied to
a uv database . The default is not to apply any smoothing.
The elements of SMOOTH are as follows:
SMOOTH(1) = type of smoothing to apply: 0 => no smoothing
To smooth before applying bandpass calibration
1 => Hanning, 2 => Gaussian, 3 => Boxcar, 4 => Sinc
To smooth after applying bandpass calibration
5 => Hanning, 6 => Gaussian, 7 => Boxcar, 8 => Sinc
SMOOTH(2) = the "diameter" of the function, i.e. width
between first nulls of Hanning triangle and sinc
function, FWHM of Gaussian, width of Boxcar. Defaults
(if < 0.1) are 4, 2, 2 and 3 channels for SMOOTH(1) =
1 - 4 and 5 - 8, resp.
SMOOTH(3) = the diameter over which the convolving
function has value - in channels. Defaults: 1,3,1,4
times SMOOTH(2) used when input SMOOTH(3) < net
SMOOTH(2).
UVRANGE....(Minimum,Maximum) baseline (kilo-lambda) to process.
SOLINT.....The interval over which the rms is determined.
0 => 60 seconds.
BPARM......Task enrichment parameters:
BPARM(1)...The fraction of baselines which can exceed the rms
limit before the integration is listed as bad.
0 => 0.25
BPARM(2)...The maximum allowable sine/cosine rms per
baseline/correlator. No default.
BPARM(3)...Source amplitude coefficient for determining bad
baselines. The maximum allowed rms is given by:
sqrt (BPARM(2)**2 + (avg_amp*BPARM(3))**2)
Note: the value of BPARM(3) is a compromise between
false detection of interference on strong sources
and missing interference on weak sources as the
interference may mimic a strong source.
DOCRT......False (<= 0) use the line printer if OUTPRINT = ' '
else write named OUTPRINT file only.
True (> 0) use the terminal interactively. The task will
use the actual terminal width as a display limit
unless 72 < DOCRT < width. In that case, the display
limit will be DOCRT characters.
OUTPRINT...Disk file name in which to save the line printer output.
' ' => use scratch and print immediately for interactive
jobs - batch jobs use OUTPRINT = 'PRTFIL:BATCHjjj.nnn'
(jjj= job #, nnn = user #). When OUTPRINT is not blank,
multiple outputs are concatenated, and the file is not
actually printed.
BADDISK...This array contains the numbers of disks on which
it is desired that scratch files not be located.
BADDISK has no effect input data.
EXPLAIN SECTION
RFI: Task to find periods of interference
Documentor: W. D. Cotton NRAO
Related Programs: TVFLG, UVFLG
The purpose of this task to to find periods of interference
based on high values of the RMS of either the sine or cosine
parts of the visibilities in a given interval. Each baseline
and correlator is analysed separately and if the fraction of
baselines on a given correlator (e.g. IF 2, channel 1, RR)
exceeds a specified level this interval is listed in the output.
Correlators
Correlators are specified by a correlator number. This
number is the number in a sequence with polarization (RR, LL,
RL, LR) varying the fastest, then frequency channel, then IF.
For VLA continuum data correlator 6 is IF 2 LL.