AIPS HELP file for FRING in 31DEC22
As of Wed Jan 26 23:31:34 2022
FRING: Task to fringe fit data
Input uv data.
INNAME UV file name (name)
INCLASS UV file name (class)
INSEQ 0.0 9999.0 UV file name (seq. #)
INDISK 0.0 9.0 UV file disk drive #
Data selection (multisource):
CALSOUR Calibrator sources
QUAL -10.0 Calibrator qualifier -1=>all
CALCODE Calibrator code ' '=>all
SELBAND Bandwidth to select (kHz)
SELFREQ Frequency to select (MHz)
FREQID Freq. ID to select.
TIMERANG Time range to use.
BCHAN 0.0 2048.0 Lowest channel number 0=>all
ECHAN 0.0 2048.0 Highest channel number
CHINC 0.0 Spectral channel increment
(data are averaged)
ANTENNAS Antennas to select. 0=all
DOFIT Subset of ANTENNAS list
for which solns are desired.
SUBARRAY 0.0 1000.0 Subarray, 0=>all
UVRANGE Range of uv distance for full
WTUV Weight outside UVRANGE 0=0.
WEIGHTIT 0.0 3.0 Modify data weights function
Cal. info for input:
DOCALIB -1.0 101.0 > 0 calibrate data & weights
> 99 do NOT calibrate weights
GAINUSE CL 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.
CLEAN map (optional)
IN2NAME Cleaned map name (name)
IN2CLASS Cleaned map name (class)
IN2SEQ 0.0 9999.0 Cleaned map name (seq. #)
IN2DISK 0.0 9.0 Cleaned map disk unit #
INVERS -1.0 46655.0 CC file version #.
NCOMP # comps to use for model.
1 value per field
FLUX Lowest CC component used.
NMAPS 0.0 4096.0 No. Clean map files
CMETHOD Modeling method:
CMODEL Model type: 'COMP','IMAG'
'SUBI' (see HELP re images)
SMODEL Source model, 1=flux,2=x,3=y
See HELP SMODEL for models.
Output uv data file.
DOAPPLY -1.0 1.0 >= 0 write output
OUTNAME UV file name (name)
OUTCLASS UV file name (class)
OUTSEQ -1.0 9999.0 UV file name (seq. #)
OUTDISK 0.0 9.0 UV file disk drive #
Solution control adverbs:
REFANT Reference antenna
SEARCH 0.0 1000.0 Prioritized reference antenna
list - supplements REFANT
- but only if APARM(9)>0
SOLINT Solution interval (min)
0 => 10 min
SOLSUB Solution subinterval
SOLMIN Min solution interval
APARM General parameters
1=min. no. antennas
2 > 0 => data divided
3 > 0 => avg. RR,LL
4 > 0 => avg. freq. in IFs
5 = 0 solve IFs separately
= 1 => combine all IFs
= 2 => also MB delay
= 3 => combine IFs in
= 4 => combine IFs in
= N => combines IFs in
< 0 => use BPARM
SEE HELP WARNING
6=print level, 1=some
7=SNR cutoff (0=>5)
8=max. ant. # (no AN)
9 > 0 => do exhaustive
10 > 0 -> fit dispersion
and IF group delay after
fit of SB delays
DPARM Delay-rate parameters
1=no. bl combo. (def=3)
2=delay win (nsec), if <0
no delay search done
3=rate win (mHz)
4=int. time (sec)
0 => min. found in data
5 >0 => don't do ls. soln
6 <0 => average in freq
7 >0 => don't rereference
8 > 0 => activate zero'ing
9 > 0 => do not fit rate
BPARM 0.0 BPARM(i) = highest IF in i'th
group if (APARM(5) < 0)
SNVER -1.0 46655.0 Output SN table, 0=>new table
ANTWT Ant. weights (0=>1.0)
BIF First IF included when
APARM(5) > 0
EIF Last IF included when
APARM(5) > 0
BADDISK 0.0 15.0 Disk no. not to use for
Task: This task determines the group delay and phase rate calibration
to be applied to a uv data set given a model of the source(s).
The output data will have the corrections applied for a single
source input file; and a solution (SN) table will be left for a
multi source data set. SN tables will be attached to the INPUT
Model images made with both values of IMAGR's DO3DIMAG
option are handled correctly, as are multi-scale images. Set
NMAPS = NFIELD * NGAUSS.
FRING now uses dynamic memory throughout, allowing large
delay-rate searches no matter what size the pseudo AP may be.
Of course, your computer must have enough memory to support
The SNR is written to the SN table as the weights. The
reference antenna is assigned a weight of SNRmin + 1 (APARM(7)+1
or 6 by default). The weight is set to 0 for solutions with
SNR < SNRmin. Note that in CALIB antennas with weight
SNRmin+1 are suspect, but they are definitely good in FRING.
The weights may now be used for editing in EDITA.
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.
The following are used for multisource data files only:
CALSOUR....List of sources for which calibration constants are to be
determined, i.e. the calibrator sources All ' ' = all
sources; a "-" before a source name. means all except ANY
source named. Note: solutions for multiple sources can
only be made if the sources are point sources at their
assumed phase center and with the flux densities given in
the source (SU) table.
QUAL.......Only sources with a source qualifier number in the SU table
matching QUAL will be used if QUAL is not -1.
CALCODE....Calibrators may be selected on the basis of the calibrator
' ' => any calibrator code selected
'* ' => any non blank code (cal. only)
'-CAL' => blank codes only (no calibrators)
anything else = calibrator code to select.
NB: The CALCODE test is applied in addition to the other
tests, i.e. CALSOUR and QUAL, in the selection of sources
for which to determine solutions.
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, 0=> all
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, 0=> all
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
override that of FREQID, however setting SELBAND and
SELFREQ may result in an ambiguity, in which case the task
will request that you use FREQID.
TIMERANG...Time range of the data to be used. In order: Start day,
hour, min. sec, end day, hour, min. sec. Days relative to
BCHAN......First channel to use. 0=>all.
ECHAN......Highest channel to use. 0=>all higher than BCHAN
CHINC......Channel increment in fitting - note channels are averaged
BCHAN to BCHAN+CHINC-1, BCHAN+CHINC to BCHAN+2*CHINC-1,
etc. This reduces the memory requirements and is
suitable for delay errors that are not too large to cause
channel-to-channel loss of coherence.
ANTENNAS...A list of the antennas to have solutions determined. If
any number is negative then all antennas listed are NOT to
be used to determine solutions and all others are. All 0 =>
DOFIT......A list of the antennas for which solutions should or
should not be determined. If DOFIT = 0, all antennas are
solved for. If any entry <= -1, , then DOFIT is taken as
the list of antennas for which no solution is desired; a
solution is found for all antennas not in DOFIT. If any
entry of DOFIT is non-zero and all are >= 0, then only
those antennas listed in DOFIT will be solved for - all
other selected antennas will not be solved for.
NOTE: THIS OPTION MUST NOT BE USED UNLESS YOU UNDERSTAND
IT FULLY. Basically, it should be used to solve for the
gains of "poor" antennas after the "good" antennas have
been fully calibrated. Antennas included in ANTENNAS but
not in DOFIT are assumed to have a complex
gain/delay/rate of (1,0,0,0) and the gains/delays
produced will be very wrong if this is not the case.
See HELP DOFIT.
The following may be used for all data files (except as noted):
SUBARRAY...Subarray number to use. 0=>all.
UVRANGE....The range of uv distance from the origin in kilowavelengths
over which the data will have full weight; outside of this
annulus in the uv plane the data will be down weighted by a
factor of WTUV.
WTUV.......The weighting factor for data outside of the uv range
defined by UVRANGE.
WEIGHTIT...If > 0, change the data weights by a function of the
weights just before doing the solution. Choices are:
0 - no change weighting by 1/sigma**2
1 - sqrt (wt) weighting by 1/sigma may be more stable
2 - (wt)**0.25
3 - change all weights to 1.0
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).
Done before determining solutions.
GAINUSE....(multisource) version number of the CL table to apply to
the data. 0 => highest.
DOPOL......If > 0 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
DOBAND.....(multi-source) 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
(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
BPVER......(multi-source) version of the BP table to be applied.
0 => highest; < 0 => no bandpass correction 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
The following specify a CLEAN model to be used if a single source was
specified in CALSOUR:
IN2NAME....Cleaned map name (name). Standard defaults.
Note: a CLEAN image for only a single-source may
be given although it may be in a multi-source file.
If the source table contains a flux, then that flux will
be used to scale the components model to obtain the
stated total flux. This is needed since initial Cleans
may not obtain the full flux even though they represent
all the essentials of the source structure.
IN2CLASS...Cleaned map name (class). Standard defaults.
IN2SEQ.....Cleaned map name (seq. #). 0 -> highest.
IN2DISK....Disk drive # of cleaned map. 0 => any.
INVERS.....CC file version #. 0=> highest numbered version
NCOMP......Number of Clean components to use for the model, one
value per field. If all values are zero, then all
components in all fields are used. If any value is not
zero, then abs(NCOMP(i)) (or fewer depending on FLUX and
negativity) components are used for field i, even if
NCOMP(i) is zero. If any of the NCOMP is less than 0,
then components are only used in each field i up to
abs(NCOMP(i)), FLUX, or the first negative whichever
comes first. If abs(NCOMP(i)) is greater than the number
of components in field i, the actual number is used. For
NCOMP = -1,0
says to use one component from field one unless it is
negative or < FLUX and no components from any other
field. This would usually not be desirable.
NCOMP = -1000000
says to use all components from each field up to the
first negative in that field.
NCOMP = -200 100 23 0 300 5
says to use no more than 200 components from field 1, 100
from field 2, 23 from field 3, 300 from field 5, 5 from
field 6 and none from any other field. Fewer are used if
a negative is encountered or the components go below
FLUX.......Only components > FLUX in absolute value are used in the
NMAPS......Number of image files to use for model. For multi-scale
models, set NMAPS = NFIELD * NGAUSS to include the Clean
components of the extended resolutions. If more than one
file is to be used, the NAME, CLASS, DISK and SEQ of the
subsequent image files will be the same as the first file
except that the LAST 3 or 4 characters of the CLASS will
be an increasing sequence above that in IN2CLASS. Thus,
if INCLASS='ICL005', classes 'ICL005' through 'ICLnnn'
or 'ICnnnn', where nnn = 5 + NMAPS - 1 will be used. Old
names (in which the 4'th character is not a number) are
also supported: the last two characters are '01' through
'E7' for fields 2 through 512. In old names, the highest
field number allowed is 512; in new names it is 4096.
CMETHOD....This determines the method used to compute the model
'DFT' uses the direct Fourier transform, this method is
the most accurate.
'GRID' does a gridded-FFT interpolation model computation
' ' allows the program to use the fastest method
CMODEL.....This indicates the type of input model; 'COMP' means that
the input model consists of Clean components, 'IMAG'
indicates that the input model consists of images.
'SUBI' means that the model consists of a sub-image of
the original IMAGR output. If CMODEL is ' ' Clean
components will be used if present and the image if not.
SUBI should work for sub-images made with DO3DIM true and
sib-images of the central facet made with DO3DIM false,
but probably will not work well for shifted facets with
DO3DIM false. Use BLANK rather than SUBIM in such cases.
CALIB will set a scaling factor to correct image units
from JY/BEAM to JY/PIXEL for image models. If the source
table contains a flux, then that flux will be used to
scale the components model to obtain the stated total
flux. This is needed since initial Cleans may not obtain
the full flux even though they represent all the
essentials of the source structure.
SMODEL.....A single component model to be used instead of a CLEAN
components model; if abs (SMODEL) > 0 then use of this
model is requested.
SMODEL(1) = flux density (Jy)
SMODEL(2) = X offset in sky (arcsec)
SMODEL(3) = Y offset in sky (arcsec)
SMODEL(4) = Model type:
0 => point model
1 => elliptical Gaussian and
SMODEL(5) = major axis size (arcsec)
SMODEL(6) = minor axis size (arcsec)
SMODEL(7) = P. A. of major axis (degrees)
2 => uniform sphere and
SMODEL(5) = radius (arcsec)
The following specify the output file to be written if the input file is
a single source file.
DOAPPLY....< 0 -> do not write the output file.
OUTNAME....Output UV file name (name). Standard defaults.
OUTCLASS...Output UV file name (class). Standard defaults.
OUTSEQ.....Output UV file name (seq. #). 0 => highest unique
OUTDISK....Disk drive # of output UV file. 0 => highest
disk number with space
The following control how the solutions are done, if you don't
understand what a parameter means leave it 0 and you will probably get
what you want.
REFANT.....The desired reference antenna for phases.
SEARCH.....List of Prioritized antennas to be used when APARM(9)>0.
This adverb supplements REFANT. Along with APARM(9)>0,
it is recommended that SEARCH be filled
with a list of antennas whose order reflects the user's
notion of which baselines will be easiest to find fringes
on. All baselines to each antenna in SEARCH will be
searched in order looking for fringes. All remaining
baselines will then be searched. Choosing SEARCH wisely
will speed the FFT portion of FRING. The antenna chosen
in REFANT is treated as SEARCH(0), ie all baselines to
it are searched first.
SOLINT.....The solution interval (min.) You really should set this;
longer values are allowed beginning with 15OCT96.
0 => 10 minutes for all inputs
If SOLINT > Scan/2 (in Multisource) SOLINT = Scan.
SOLSUB.....The begin time for the next interval in advanced from the
current one by SOLINT / SOLSUB where 1 <= SOLSUB <= 10.
0 -> 1. This is to produce solutions at sub-intervals of
SOLINT based on SOLINT length of averaging.
SOLMIN.....Minimum number of subintervals to be used in a solution.
0 -> SOLSUB.
APARM......General control parameters.
APARM(1)...Minimum number of antennas allowed for a solution. 0 => 3.
APARM(2)...If > 0 then the input data has already been divided by a
model; only solutions will be determined.
APARM(3)...If > 0 then average RR, LL
APARM(4)...If > 0 average all frequencies in each IF before the
solution and in the output for single source files.
APARM(5)...WARNING: IF THE FREQUENCY INCREMENT BETWEEN IFS THAT WILL
BE INCLUDED IN A GROUP HAS THE OPPOSITE SIGN FROM THE
FREQUENCY INCREMENT BETWEEN CHANNELS IN THE IFS OF THAT
GROUP, YOU SHOULD NOT USE THE FOLLOWING
(SET APARM(5)=0 ONLY).
If < 0, use BPARM to define the grouping of IFs.
If = 0 then make separate solutions.
If = 1 then make a combined solution for the IFs;
If = 2 do separate least squares fits for single- and
multi-band delays. This option will override APARM(4)
> 0. WARNING: multi-band delays derived by this method
cannot be smoothed. The SB delay will be the same
in each IF but will differ from the MB delay. The
latter is not used in AIPS calibration but is used
by non-AIPS astrometric software.
If = 3 then make solutions combining IFs 1 through NIF/2
and IFs NIF/2+1 through NIF. This may be appropriate
for the EVLA in which the first NIF/2 are from
hardware IF AC and the others are from hardware BD.
If = N then make solutions combining IFs in groups of
NIF/(N-1) channels. Note that NIF should be an
integer multiple of (N-1). This may be appropriate
for various configurations of the EVLA correlator.
NOTE - APARM(10) can partly override this - causing the
task to fit a delay in each IF and then to fit a
dispersion across all IFs plus delay for each group of
IFs. The output SN table will contain dispersion values
plus the single-band delays and phases corrected for the
APARM(6)...Print flag, -1=none, 0=time every 10th time, 1=time,some
info, 2=more including the antenna signal to noise ratio,
3=a very great deal.
APARM(7)...The minimum allowed signal-to-noise ratio. 0 => 5
APARM(8)...If there is no antenna (AN) table with the input file then
the maximum antenna number in the file should be entered in
APARM(9)...If > 0, perform exhaustive baseline search in the initial
FFT stage. Normally, the first stage of FRING is to FFT
individual baselines searching for initial estimates of the
residual phases, rates, and delays. This stage is notable
in that FRING gives up too easily - only baselines to the
user-selected REFANT and one other antenna are searched.
APARM(9)>0 instructs FRING to exhaustively search for
initial estimates for each antenna's errors. See SEARCH
above as well.
APARM(10)..If > 0, causes the task to fit a delay in each IF and then
to fit a dispersion plus a delay for each group of IFs to
the SB delays in all IFs. The output SN table will
contain dispersion values plus the single-band delays and
phases corrected for the dispersion. If only one group
of IFs was used, the multi-band delay is also returned.
(More than 1 group means there is not a multi-band
Delay-rate control parameters:
DPARM......Delay rate parameters.
DPARM(1)...Number of baseline combinations to use in the initial,
coarse fringe search (1-3). Larger values increase the
point source sensitivity but reduce the sensitivity to
extended sources when an accurate model is not available.
DPARM(2)...The delay window to search (nsec) centered on 0 delay.
0 => full Nyquist range defined by the frequency spacing.
If DPARM(2) < 0.0 no delay search will be performed.
DPARM(3)...The rate window to search (mHz) centered on 0 rate.
0 => full Nyquist range defined by the integration time.
DPARM(4)...The minimum integration time of the data (sec);
0 => search the data to find the minimum integration
The correct minimum of all baselines should be supplied.
DPARM(5)...If > 0 then don't do the least squares solution. If the
least squares solution is not done then only the coarse
search is done and much less accurate solutions are
DPARM(6)...If >= 0 then the output data will not be averaged in
frequency else, all frequencies in each IF will be
averaged. Affects single source files only.
DPARM(7)...If > 0 then the phase, rate and delays will not be
re-referenced to a common antenna. This option is only
desirable for VLBI polarization data.
DPARM(8)...DPARM(8)>0 allows zero'ing of RATE, DELAY, and/or PHASE
solutions. ** Note that the ZEROing is done _AFTER_ the
FRING solution is found, this is not the mechanism for
turning off the DELAY, RATE, or PHASE search, see
DPARM(2-3) for that capability. **
DPARM(8) value zero RATES? zero DELAYs? zero PHASEs?
0 No No No
1 Yes No No
2 No Yes No
3 Yes Yes No
4 No No Yes
5 Yes No Yes
6 No Yes Yes
7 Yes Yes Yes
DPARM(9)...> 0 or (= 0 and EVLA) => supress fitting for rate (rather
than just zero the fit afterwards). This assumes that
the true rate is small and causes all the data in SOLINT
to be averaged before being fed to the fitter.
DPARM(8)=1 is not needed in this case.
If you want rates for the EVLA, set DPARM(9)=-1.
BPARM......If APARM(5) < 0, group the IFs such that BPARM(i) defines
the highest IF in group i. This means that BPARM(i+1)
must be > BPARM(i) and the first BPARM not to meet this
rule defines the number of groups. Note that that really
should be the maximum IF in the data set.
SNVER......Desired output SN table. Solutions will be added to the
specified table replacing any previous solutions for the
same TIMERANG, CALSOUR etc. 0 means create a new SN table.
ANTWT......Antenna weights. These are additional weights to be
applied to the data before doing the solutions, one per
antenna. Use PRTAN to determine which antenna numbers
correspond to which antennas.
BIF........First IF included when APARM(5)=1,3,4 (all IFs receive the
solution found for the appropriate group of IFs, but only
BIF-EIF are used to find it).
EIF........Last IF included when APARM(5)=1,3,4 (all IFs receive the
solution found for the appropriate group of IFs, but only
BIF-EIF are used to find it).
BADDISK....A list of disk numbers to be avoided when creating scratch
For some basic introduction to fringe fitting, please see the discussions
Thompson, Moran, and Swenson
Felli and Spencer
Perley, Schwab, and Bridle
The AIPS CookBook also describes how and when FRING should be used.