AIPS HELP file for SNSMO in 31DEC24
As of Fri Apr 19 9:23:33 2024
SNSMO: Task which smooths and filters solution (SN) tables
INPUTS
INNAME Input UV file name (name)
INCLASS Input UV file name (class)
INSEQ 0.0 9999.0 Input UV file name (seq. #)
INDISK 0.0 9.0 Input UV file disk unit #
SOURCES Source list ' '=>all.
DOBTWEEN -1.0 1.0 > 0 -> smooth all sources
together; else separate them
SELBAND Bandwidth to select (kHz)
SELFREQ Frequency to select (MHz)
FREQID Freq. ID to select, 0=>all
BIF 0.0 100.0 Lowest IF number 0=>all
EIF 0.0 100.0 Highest IF number 0=>all
TIMERANG Time range to use.
ANTENNAS Antennas to correct.
SUBARRAY 0.0 9999.0 Subarray; 0 => all.
SAMPTYPE Smoothing function: BOX, MWF,
GAUS, EXP, LINE, 2PT, 2PTH
BPARM Smoothing parameters
(1-5) support, (6-10) FWHM
for amp,phase,rate,delay,MBD
CUTOFF 0.0 Cutoff for functional forms
DOBLANK Blanked value interpolation
SMOTYPE Data to smooth: AMPL, PHAS,
BOTH, DELA, VLBI, VLRI, VLMB,
VLDE
CPARM Range of allowed delays and
rates.
DELCORR Allowed range of dispersion
NPIECE 0.0 Number IF groups used in
FRING (re APARM(5))
NORMALIZ -1.0 4.0 > 0 => apply a global
normalization; = 0 adjust a
pre-existing normalization
INVERS Input SN table; 0=>highest
OUTVERS Output SN table; 0=>new
REFANT Reference antenna 0=>pick.
BADDISK 0.0 9999.0 Disks to avoid for scratch
HELP SECTION
SNSMO
Task: This task references and smooths an SN table. First rates and
delays can be clipped to a specified range of values. Next phase
like values (phase, delays and rate) are rereferenced if necessary
to a single antenna. This rereferencing is done in a manner which
should preserve the coherence of the two orthoginal polarization
systems.
Following the referencing the solutions are smoothed in a manner
to preserve coherence, rates may be averaged before smoothing and
the average phase difference between the orthogonal polarizations
before smoothing is enforced on the solutions after smoothing.
Blanked solutions will be interpolated or not under control of
DOBLANK.
WARNING: THIS TASK WAS CHANGED 27 MARCH, 2003. The smoothing no
longer propagates good solutions indefinitely. Instead the support
size is strictly enforced. Additional smoothing options are now
available. DOBLANK is now changed: if it is < 0, failed solutions
are not fixed, if it is >= 0 they are fixed. If it is <= 0, good
solutions are smoothed, if it is > 0 good solutions are not
altered.
Adverbs:
INNAME.....Input UV file name (name). Standard defaults.
INCLASS....Input UV file name (class). Standard defaults.
INSEQ......Input UV file name (seq. #). 0 => highest.
INDISK.....Disk drive # of input UV file. 0 => any.
SOURCES....list of sources to process: '*' = all;
a "-" before a source name means all except ANY source
named.
DOBTWEEN...> 0 => smooth all SN values regardless of source.
<= 0 => smooth only SN values from the same source.
Well-separated calibrators may have different phases just
because of different atmosphere, so one would not want to
smooth them together. This can be achieved via doing one
source at a time, but DOBTWEEN allows one to do all
sources at once - at least if the choice is a simple one.
FREQID.....Frequency identifier to select (you may determine which
is applicable from the OPTYPE='SCAN' listing produced by
LISTR).
BIF........First IF to process. 0=>all. Set to 1 for VLMB and VLDE.
EIF........Highest IF to process. 0=>all higher than BIF
Set to all for VLMB, VLDE.
TIMERANG...Time range of the data to be used. In order:
Start day, hour, min. sec, end day, hour, min. sec.
Days relative to reference date.
ANTENNAS...A list of the antennas to be modified. If any number is
negative then all antennas listed are NOT to be modified.
All 0 => use all.
SUBARRAY...The subarray to modify. 0 -> all.
SAMPTYPE...The type of smoothing.
'BOX ' = boxcar smoothing (default)
'MWF ' = Median window filter
'GAUS' = Gaussian
'EXP ' = Exponential
'LINE' = Linear (1 - abs(t-t0)/sigma)
'2PT ' = Two-point
'2PTH' = Two-point + "Hanning"
BPARM......Parameters for smoothing function.
Function support full-width width in hours.
(1) => support time for amplitudes (hours),
(2) => support time for phase (hours),
(3) => support time for rates (hours),
(4) => support time for singleband delay (hours),
(5) => support time for multiband delay, dispersion
(hours)
Added parameter (FWHM) for GAUS, EXP, LINE
(6) => smoothing FWHM time for amplitudes,
(7) => smoothing FWHM time for phase,
(8) => smoothing FWHM time for rates
(9) => smoothing FWHM time for singleband delay
(10) => smoothing FWHM time for multiband delay,
and dispersion
In all cases, the substitution for blanked and good
solutions is governed by DOBLANK (see below)
CUTOFF.....Cutoff for GAUS, EXP, LINE. The sum of the weighting
function in the support region must exceed CUTOFF for the
smoothed value to be regarded as valid. Be careful, a
value of 1.5 means that the sample itself must be good
and the sum over other good samples in the support range
must exceed 0.5. < 1.e-6 => 1.e-6.
DOBLANK....Blanked value interpolation:
> 0: replace previously blanked values with smoothed
values, leave previously good values unchanged.
= 0: replace previously blanked and previously good
values with smoothed values.
< 0: replace previously good values with smoothed values,
leave previously blanked values blanked.
Note that DOBLANK >= 0 requires a SMOTYPE that smooths
both phase and amplitude, namely BOTH, FULL, VLBI, or
VLMB.
SMOTYPE....Specified the data to be smoothed. ' '=>'AMPL'
'AMPL' = amplitude smoothing only,
'PHAS' = phase smoothing only,
'BOTH' = amplitude and phase,
'DELA' = delay smoothing only,
'VLBI' = Coherent phase, rate and delay smoothing.
Phases smoothed in each IF separately.
'VLRI' = Coherent phase, rate and delay smoothing.
Phases smoothed in each IF separately, but
rates are averaged over IF as well as
polarization.
'VLMB' = Like VLBI and VLRI but phases are averaged
over IF after correction for multi-band delay,
before smoothing. The average phase is the
phase of vector average of the complex
amplitudes. The average amplitude is the
scalar average of the amplitudes.
'VLDE' = Like VLMB but phases of the first IF in each
piece (group of IFs) are smoothed and then the
phases in all other IFs in that group are
computed from the first IF and the smoothed
delays. Thus iF the phase difference from one
IF to the next is due solely to delay (FRING
included both IFs in a single group) you
should use this option abd set NPIECE
carefully.
'FULL' = same as VLBI
CPARM......Data can be clipped by comparison with a median window
filter. The width of the Median window is specified in
CPARM(1-5). The maximum allowed deviation is given in
CPARM(6-10). 0 => all values are OK.
(1) => smoothing time for amplitudes (hours),
(2) => smoothing time for phase (hours)
(3) => smoothing time for rates (hours)
(4) => smoothing time for singleband delay (hours)
(5) => smoothing time for multiband delay, dispersion
(hours)
(6) => Max. deviation for amplitudes,
(7) => Max. deviation for phase, (deg)
(8) => Max. deviation for rates (mHz)
(9) => Max. deviation for singleband delay (nsec)
(10) => Max. deviation for multiband delay (nsec)
The clipping on rates is based on the MWF of the average
rate over IF compared to the individual rates. The
amplitude, phase, and SB delay are done one IF at a
time.
DELCORR....The clip level for deispersion (ns/m/m).
NPIECE.....The IFs were combined in FRING into NPIECE pieces under
control of APARM(5). <=0 -> NIF. This helps handle
phase when smoothing delay so set this carefully. Note:
NPIECE = 1 for APARM(5) = 1 or 2. NPIECE = APARM(5)-1
for APARM(5) > 2 in FRING.
NORMALIZ...Controls whether a global gain normalization is applied
to the table. If there was one previously and NORMALIZ=0
or if NORMALIZ > 0, a global normalization is applied.
Otherwise, the global normalization parameter is left
unchanged.
INVERS.....input version number of the SN table to smooth.
0 => Highest.
OUTVERS....output version of SN table to write.
0 => create new table.
REFANT.....Reference antenna to use. All phase-like values in the
SN table will be referenced to this antenna. 0=> use the
one used in the most solutions.
BADDISK....A list of disks on which scratch files are not to be
placed. This will not affect the output file.
EXPLAIN SECTION
SNSMO: Smooths solution (SN) tables.
Documentor: W. D. Cotton
Related Programs: CALIB, FRING, CLCAL, SNCOR
This task re-references an SN table to a common antenna (REFANT)
and then allows smoothing of a variety of data types in an solution
(SN) table. This re-referencing and smoothing is done in a way that
will maintain phase coherence between the right and left (or
orthogonal linear) systems.
Phase smoothing is done after removing the integral of the fringe
rate which is then replaced after smoothing. This allows the
possibility of sensible phase smoothing with non-zero fringe rates. It
is recommended that this task not overwrite the original table to
protect aginst errors.
The SN table differs from the standard SN table by the inclusion
of multiband delays for the two polarizations and the IF phases are at
the IF frequency.
SMOTYPE = 'VLBI'
This option causes the residual rates for R and L polarizations
to be averaged to maintain R-L coherence. The rates in each IF are
processed independently. Values in the "Multiband" delay columns will
be processed but the phases in each IF are processed independently.
SMOTYPE = 'VLRI'
This option causes all residual rates for a given time and
antenna to be averaged over both IF and polarization and the phases
for the two polarizations of a given IF are forced to maintain R-L
coherence. Values in the "Multiband" delay columns will be processed
but the phases in each IF are processed independently.
SMOTYPE = 'VLDE'
This option is designed for data which has been fringe fitted for
delays in groups of IFs (FRING APARM(5) > 0). In this case the phase
in each IF should be the sum of the phase of the first IF in the group
and the product of the delay times the frequency difference of that IF
and the first IF of the group. The phase of that first IF in each
group is smoothed and then the phases for the other IFs in the group
are determined from the smoothed delays. Amplitudes, delays, and
rates are set as in VLMB. This is the recommended approach when you
have done groups including a single group (the multi-band delay
method). Note that you must set NPIECE carefully for this option -
use MAX (1, APARM(5)-1).
SMOTYPE = 'VLMB'
This option is designed for data which has been fringe fitted for
a multiband delay. In this case the phase in each IF should be
estimates of the same (or identical) values. Thus the phases are
corrected for the multi-band delay and then averaged in IF before
smoothing. The average phase is the phase of vector average of the
complex amplitudes to which the phase due to the multi-band delay is
restored.. The amplitude is the scalar average of the amplitudes.
SAMPTYPE
'2PT ' - interpolates in time between the two nearest neighbors of
a flagged sample within the support time range
This mode is really only for DOBLANK > 0.
'2PTH' - interpolates in time between the two nearest neighbors of
a sample within the support time range, then averages the
sample (if good) with the interpolated value. When there
is only one good neighbor, the sample itself counts
double if it is good.