AIPS HELP file for IMFRING in 31DEC24
As of Fri Apr 26 11:03:37 2024
IMFRING: Determines antenna delays from large image
INPUTS
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 #
input image
IN2NAME Large image name (name)
IN2CLASS Large image name (class)
IN2SEQ Large image name (seq #)
IN2DISK Large image name (disk)
BLC 0.0 4096.0 Bottom left corner of image
0=>1
TRC 0.0 4096.0 Top right corner of image
0=>max allowed
ICUT 0.0 Include all points > ICUT in
absolute value only
FLUX Discard all points < FLUX
NX 1.0 Number panels in X
NY 1.0 Number panels in Y
OUTNAME name to use for temporary
files (CC, OOSUB output)
OUTDISK Disk to put subimages/CCs
Solution control adverbs:
DOKEEP -1.0 1.0 > 0 -> keep divided us data
Data selection (multisource):
BCHAN 0.0 2048.0 Lowest channel number 0=>all
ECHAN 0.0 2048.0 Highest channel number
ANTENNAS Antennas to select. 0=all
DOFIT Subset of ANTENNAS list
for which solns are desired.
UVRANGE Range of uv distance for full
weight
WTUV Weight outside UVRANGE 0=0.
WEIGHTIT 0.0 3.0 Modify data weights function
INVERS -1.0 46655.0 CC file version #.
ONEFREQ -1.0 1.0 > 0 => CC model from only
one frequency (group)
CMETHOD Modeling method:
'DFT','GRID',' '
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 = 1 => combine all IFs
= 2 => also MB delay
= 3 => combine IFs in
halves
= 4 => combine IFs in
thirds
= N => combines IFs in
N-1 pieces
SEE HELP WARNING
6=print level, 1=some
7=SNR cutoff (0=>5)
8=max. ant. # (no AN)
9 > 0 => do exhaustive
baseline search
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 => don't avg. in freq
7 >0 => don't rereference
phase
8 > 0 => activate zero'ing
options
9 > 0 => do not fit rate
ANTWT Ant. weights (0=>1.0)
BIF First IF included when
APARM(5) > 0
EIF Last IF included when
APARM(5) > 0
BPARM Task enrichment parameters
(1) Antenna diameter (m)
0 -> no correction
(2) Omit CC options
(3) spectral index radius
0 -> no correction
FQTOL Frequency tolerance in kHz
(primary beam & spec index)
IN3NAME Spectral index image name
IN3CLASS Spectral index image class
IN3SEQ Spectral index image sequence
number
IN3DISK Spectral index image disk
IN4NAME Spectral curvature name
IN4CLASS Spectral curvature class
IN4SEQ Spectral curvature sequence
number
IN4DISK Spectral curvature disk
BADDISK 0.0 15.0 Disk no. not to use for
scratch files.
HELP SECTION
IMFRING
Task: IMFRING is a procedure that combines IM2CC, OOSUB, FRING, and
finally TACOP. IM2CC breaks a large (usually CASA) image into
pieces, making both an image and a Clean components table for
each piece. This is needed to allow AIPS to use its geometries
while CASA has used the W-projection geometry. OOSUB divides
the data for a calibration source by the model from these
pieces plus options to permit frequency-dependent primary beam
and spectral index corrections. CALIB then determines an
IF-dependent delay and phase, using the divided data. A
solution (SN) table is written and copied to the input uv file
by TACOP. Finally the temporary, divided data set is deleted
(optionally) and the image pieces are deleted..
This procedure does not apply data selection and calibration
adverbs to the input data set. You must apply these with SPLIT
or SPLAT (or other tasks) to make a data set consisting solely
of the edited/calibrated data that you wish to self-cal.
IMFRING makes a number of temporary files all of which are
assigned specific names including sequence number 1. It will
check for the presence of any of these on your disks before
doing work. If any are present, IMSCAL will list them and
quit, allowing you to rename them or delete them.
This procedure is obtained by entering RUN OOCAL.
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.
**** Model image in Jy/pixel (not convolved with beam) ****
IN2NAME....Input image file name (name). Standard defaults.
IN2CLASS...Input image file name (class). Standard defaults.
IN2SEQ.....Input image file name (seq. #). 0 -> highest.
IN2DISK....Disk drive # of input image. 0 -> any.
BLC........The bottom left-hand pixel of the input image which
becomes the bottom left corner of the subimage from
which the NX x NY panels are taken. 0 -> 1.
TRC........The top right-hand pixel of the input image which
becomes the top right corner of the subimage from which
the panels are taken. 0 -> max allowed value.
ICUT.......CC components are made only from pixel values greater in
absolute value than ICUT and
FLUX.......CC components are made only from pixel values greater
than FLUX (in actual value). Thus FLUX=0 cuts off all
negatives.
NX.........The X axis is divided into NX nearly equal panels.
NY.........The Y axis is divided in NY nearly equal panels.
Be sure to make enough to account for any W term issues.
OUTNAME....The output subimages are stored on OUTDISK with this name
parameter. The OUTSEQ=1 and OUTCLASS=IMCnnn. The output
from the OOSUB step in OOCAL also uses this name with
OUTCLASS 'OOCAL1'.
OUTDISK....The output subimages and CC files are put on OUTDISK, the
OOSUB output file is put on INDISK. It is better to
avoid Lustre disks for the CC files.
DOKEEP.....> 0 => keep the file produced by OOSUB containing the
input data divided by the model and the SN table
produced by CALIB
<=0 => delete this temporary file after TACOP.
BCHAN......First channel to use. 0=>all.
ECHAN......Highest channel to use. 0=>all higher than BCHAN
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 =>
use all.
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):
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
ONEFREQ....In IMAGR, a CC file is made from the "average" of all
channels included in the bandwidth synthesis. But it is
also possible to make the model image(s) from a single
frequency (or from frequencies within FQTOL anyway).
Set ONEFREQ = 1 if the model was made this way, leave it
zero if all frequencies were included in the model.
CMETHOD....This determines the method used to compute the model
visibility values.
'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
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 = 1 then make a combined solution for the IFs;
If <= 0 then make separate solutions.
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.
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 = 4 then make solutions combining IFs 1 through NIF/4,
NIF/4+1 through NIF/2, NIF/2+1 through 3*(NIF/4),
and IFs 3*(NIF/4)+1 through NIF. This may be
appropriate for the EVLA for 3-bit sampling in which
each quarter passes through separate hardware and
hence has separate delay errors.
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
dispersion.
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(8).
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.
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.
0=>3.
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
time.
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
obtained.
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 => 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.
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).
BPARM......Correction control parameters (SEE EXPLAIN IMAGR):
(1) If > 0 then make frequency dependent primary beam
corrections assuming an antenna diameter of IMAGRPRM(1)
meters. Note that VLA and ATCA arrays (TELESCOPE
header parameter) use the default primary beam
parameters defined elsewhere in AIPS, while other
antennas actually use IMAGRPRM(1) as the diameter of a
"standard" telescope. See FQTOL below also.
(2) If BPARM(1) > 0, you may omit selected CCs from the
operation based on position:
BPARM(2) <= 0 : Include all CCs
= 1 : Omit CCs within the main beam at
all frequencies
= 2 : Omit CCs within the main beam at
some frequncies
= 3 : Omit Ccs outside the main beam at
some frequencies
= 4 : Omit CCs outside the main beam at
all frequencies
(3) 1 => use a spectral-index image represented in
IN3NAME, IN3CLASS, IN3SEQ, IN3DISK below to correct the
Clean component model for each channel. IN4NAME et al
will also be used as a curvature image iff IN3NAME are
specified.
BPARM(3)-0.5 is used as a radius in pixels over which
the spectral index image is averaged. When it is small
(0 < BPARM(3) <~ 1), the spectral index is interpolated
rather than averaged. See FQTOL below as well. When
doing spectral index, the primary beam correction
(BPARM(1)) costs very little extra. This parameter is
IMAGRPRM(17) in IMAGR.
FQTOL......Frequency tolerance in kHz. Spectral channels with FQTOL
are handled together (use the same average CC model) when
applying the primary beam and spectral index
corrections. Default is to do each channel separately
which can take a long time.
IN3NAME....Image name of spectral index image; no default.
IN3CLASS...Image class of spectral index image; no default.
IN3SEQ.....Image sequence of spectral index image; 0 -> highest.
IN3DISK....Disk of spectral image image; 0 -> any.
IN4NAME....Image name of spectral index curvature image; no default.
Curvature images should be base 10 rather than base e -
they differ by a factor of 2.3. Also the reference
frequency is 1.0 GHz. These are changes done 2010-07-13.
IN4CLASS...Image class of spectral index curvature image; no
default.
IN4SEQ.....Image sequence of spectral index curvature image;
0 -> highest.
IN4DISK....Disk of spectral curvature image image; 0 -> any.
BADDISK....A list of disk numbers to be avoided when creating scratch
files.
EXPLAIN SECTION