AIPS HELP file for BLING in 31DEC24
As of Mon Apr 29 5:14:59 2024
BLING: Task to determine residual delays and rates
INPUTS
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 unit #
CALSOUR Calibrator sources
QUAL -10.0 Calibrator qualifier
-1 => all
CALCODE Calibrator code
' '=>all
STOKES Polarizations to process
TIMERANG Time range to use.
ANTENNAS Antennas to use. 0=all
BASELINE Baselines with ANTENNAS.
SUBARRAY 0.0 1000.0 Subarray. 0 => 1
SELBAND Bandwidth to select (kHz)
SELFREQ Frequency to select (MHz)
FREQID Freq. ID to select.
BIF 0.0 First IF to use 0 => 1
EIF 0.0 Last IF to use 0 => max
BCHAN 0.0 2048.0 Lowest channel number
0 => 1
ECHAN 0.0 2048.0 Highest channel number
0 => max
UVRANGE Range of uv distances to
use
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.
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:
'DFT','GRID',' '
CMODEL Model type: 'COMP','IMAG'
OPCODE Type of solution:
' ' => 'INDE'
SOLINT Solution interval (min)
INFILE Control file
APARM Task enrichment parameters:
1: minimum integration
time in sec (0 => 1.0)
2: > 0 => subtract model
3: > 0 => stack data
4: min SNR (0 => 5.0)
5: minimum coherence ( percent)
0 => 20 percent
6: delay precision tuning
(see help for BLING)
7: rate precision tuning
(see help for BLING)
DPARM Delay-rate windows:
1: multiband delay centre
2: multiband delay width
3: single-band delay ctr
4: single-band delay wdth
(delays in nanosec)
5: rate centre (mHz)
6: rate width (mHz)
7: accel. centre (uHz/sec)
8: accel. width (uHz/sec)
9: accel. step (uHz/sec)
DOUVCOMP If > 0 then use compressed
scratch files.
BADDISK List of disks not to be
used for scratch files.
HELP SECTION
BLING
Task: BLING determines the residual group delay and phase rate and
acceleration for each baseline in an array. The results are
stored in a baseline fringe solution (BS) table attached to the
uv data file. The task BLAPP will read a BS table and
distribute the baseline-based quantities between telescopes.
Model images made with both values of IMAGR's DO3DIMAG
option are handled correctly, as are multi-scale images. Set
NMAPS = NFIELD * NGAUSS.
Adverbs:
Input data file:
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.
Source selection (multisource files only):
CALSOUR....List of sources for which residual fringe
parameters are to be determined, i.e. the
calibrator sources.
If all entries are blank then all sources in the
input file will be used. If any entry is preceded
by a minus sign then all sources in the input file
other than those listed in CALSOUR will be used.
QUAL.......Only sources with a source qualifier number in the
SU table matching QUAL will be used if QUAL is not
-1. This selection criterion is applied to sources
selected using CALSOUR.
CALCODE....Calibrators may be selected on the basis of the
calibrator code:
' ' => any calibrator code selected
'* ' => any non blank code (cal. only)
'-CAL' => blank codes only (no calibrators)
anything else = calibrator code to select.
This selection criterion is applied to the sources
selected using CALSOUR and QUAL.
Note that the source selection parameters should only specify a
single source if a model is to be subtracted before searching
for fringes.
Data selection:
STOKES.....The polarizations to use. This should be a
concatenation of any of the four polarization
correlations RR, LL, RL and LR or one of
the special values 'HALF' (RR and LL) or 'CROS'
(RL and LR). Default: 'HALF'
TIMERANG...Time range of the data to be used. In order:
Start day, hour, min. sec., end day, hour, min,
sec. Days relative to the reference date of the
observations. Default: from the beginning of the
observations in the input file to the end.
ANTENNAS...A list of antennas used, in combination with
BASELINE, to select the baselines to process.
If all entries are positive include only baselines
including the listed telescopes; if any entry is
negative use all telescopes not listed.
Default: use all baselines.
BASELINE...Antennas appearing at the other end of selected
baselines from telescopes selected using
ANTENNAS. Example: to select baselines 1-6,1-8,
2-6 and 2-8 set ANTENNAS=1,2; BASELINE=6,8.
Default: use all baselines involving telescopes
selected using ANTENNAS.
SUBARRAY...Subarray number to use. Default: 1.
SELBAND....Bandwidth of the data to be selected. If more than
one IF is present SELBAND is the bandwidth of the
first IF required. Units = kHz. Default: use
FREQID.
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. Default: use
FREQID.
FREQID.....Frequency (FQ) group identifier to select (you may
determine which is applicable from the
OPTYPE='SCAN' listing produced by LISTR). If
either of SELBAND or SELFREQ are set then their
values overide that of FREQID unless SELBAND
and SELFREQ are ambiguous; if SELBAND and
SELFREQ are ambiguous then the task will request
that you use FREQID.
BIF........First IF to use. Default: 1
EIF........Last IF to use. Default: highest IF number in
file.
BCHAN......First channel to use. Default: 1
ECHAN......Highest channel to use. Default: highest channel
number in file.
UVRANGE....Range of projected spacings to be used in 1000's
of wavelengths. Default: 1.0 to 1.0E10
Calibration switches (multisource files only):
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).
GAINUSE....Version number of the CL table to apply to the
data. Default: highest version number
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......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
SMOOTH(2).
Source model to be divided into the data.
IN2NAME....Cleaned map name (name). Standard defaults.
For a single source file the model determined by
SMODEL is used instead of the CLEAN components
if IN2NAME = ' ' and IN2CLASS = ' ';
For a multi-source file a point source with flux given
in the SU table is used instead of a CLEAN components
if IN2NAME = ' ' and IN2CLASS = ' '.
Note: a CLEAN image for only a single source may
be given although it may be in a multisource file.
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
example
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.
FLUX.......Only components > FLUX in absolute value are used in the
model.
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 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.
NOTE: when using a model derived from data with
difference uv sampling it is best to use 'DFT'
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. If
CMODEL is ' ' clean components will be used if present
and the image if not.
Note: A normal CLEAN restored image is not a suitable
model as it has been tapered by the restoring beam. A
CLEANed image restored with a very small restoring beam
is usable.
Note that IMAG models are USUALLY scaled by the beam area
and CC models are scaled to match the source-table total
flux when appropriate. BLING DOES NOT DO THESE SCALINGS.
Task control:
OPCODE ....Solution type
'INDE' => independent delay and rate solutions
for each IF and polarization. Use
for multi-IF data without phase cal.
'VLBA' => single delay and rate for all IFs
in each polarization. Use for VLBA
data or any other multi-IF data with
more than one phase cal per IF.
'MK3 ' => multiband and single-band delays
and rates for all IFs in each
polarization. Use for Mk3 VLBI data
or any other multi-IF data with only
one phase cal per IF.
'RATE' => fit rate and accelerations only.
Use on one channel only when
interpolating rates from fringe
finders to program sources.
SOLINT.....Solution interval in minutes. A solution interval
may be cut short to avoid crossing a scan boundary
if an index table is present. The solution inter-
val may be overridden for particular times and
baselines in the control file. 0 -> 5 min
INFILE.....The name of a text file containing solution inter-
vals and search windows for specific baselines and
time ranges.
APARM......Miscellaneous control parameters.
APARM(1)...Minimum integration time in file in
seconds. This is used to calculate the
amount of data storage that BLING must
allocate. It is usually better to set
this too small than too large although
smaller values make it more likely that
you will run out of memory.
<= 0.0 -> 1.0 sec
APARM(2)...Model division flag. If this has a
positive value then a model will be
divided into the data before
searching for fringes.
APARM(3)...Baseline stacking flag. If this has a
positive value baseline data will be
stacked. Baseline stacking uses the
data from baselines i-k and k-j (for all
k.ne.i and k.ne.j) to increase the
sensitivity on baseline i-j. Do not
enable stacking if your file contains
multiple integration times.
APARM(4)...Minimum SNR for detection. <= 0 -> 5.0
APARM(5)...Minimum coherence value in percent. The
lowest ratio of the vector amplitude sum
and the scalar amplitude sum that will
be accepted. <= 0 -> 20 percent
APARM(6)...Delay precision control.
APARM(7)...Rate precision control.
These parameters control the amount of
padding used in the FFT searches.
>= 0 pads by a factor of 2
-1 ................... 4
-2 ................... 8
-3 ................... 16
-4 ................... 32
-5 ................... 64
-6 ................... 128
<= -7 .................... 2
Increasing the padding may give a little
extra precision but will slow BLING down
by a factor of up to (approximately)
2 ^ -(APARM(5) + APARM(6)). It is rarely
worth while to use extra padding.
DPARM......Default search windows (may be overridden in the
control file). Window widths less than or equal
to zero default to the full ambiguity range.
DPARM(1)...Multiband delay window centre (ns)
DPARM(2)...Multiband delay window width (ns)
DPARM(3)...Single-band delay window centre (ns)
DPARM(4)...Single-band delay window width (ns)
DPARM(5)...Fringe rate window centre (mHz)
DPARM(6)...Fringe rate window width (mHz)
DPARM(7)...Acceleration window centre (uHz/s)
DPARM(8)...Acceleration window width (uHz/s)
DPARM(9)...Acceleration search step (uHz/s)
DPARM(9) <= 0.0 turns off the acceleration search
unless overridden in the control file.
DOUVCOMP...UV data compression flag. If this is greater than zero
then BLING scratch files will be written in compressed
form. This reduces the amount of disk required to run
BLING but can decrease the precision of intermediate
results and can affect weighting and flagging. Avoid
compressing scratch data if your original data is
uncompressed or if you are dividing by a model unless
disk space is at a premium.
BADDISK....A list of disks not to be used for scratch files.
EXPLAIN SECTION
BLING: Task to find fringes on individual baselines.
DOCUMENTOR: Chris Flatters, NRAO
RELATED PROGRAMS: BLAPP, PRTBS, FRING
INTRODUCTION
BLING searches for fringes in residual delay and rate on
individual baselines and stores the results in a baseline
solution (BS) table attached to the uv data. These results can
be applied to the data by using BLAPP to resolve the
baseline-based quantities into antenna-based terms. This
procedure is similar to that described by Alef and Porcas
(Astron. Astrophys. vol. 168 p365, 1986).
While BLING is usually much slower than FRING, it offers a
greater level of control. Search windows and solution intervals
can be specified for individual baselines and time ranges and
BLING can search for a fringe acceleration term (the time
derivative of the residual rate).
You should normally use FRING to determine rates and delays and
restrict your use of BLING to cases where FRING may have
problems. Cases where BLING may be preferable to FRING include
the following.
* Fringe acceleration searches are needed. This is only likely
for space VLBI.
* Fringe locations can be predicted, allowing tight, off-centre
windows to be used.
* Differing baseline sensitivities make it desirable to use
different solution intervals for different baselines.
* Differing baseline sensitivities defeat FRING's strategy for
choosing baselines for the coarse search (for any given
antenna, FRING will look at the baseline from that antenna to
the reference antenna and will try a baseline to a secondary
reference if fringes are not found but will not try all
possible secondary references while BLING will examine all of
the baselines to a given telescope.
SOLUTION MODES
BLING has a number of modes which allow it to search for
different sets of fringe parameters. The mode is chosen by
setting OPCODE and the parameters to be solved for in each mode
are shown in the following table.
+------+-----------------+-------------------+------+
| Mode | Multiband delay | Single-band delay | Rate |
+------+-----------------+-------------------+------+
| INDE | no | yes | yes |
| VLBA | yes | yes | yes |
| MK3 | yes | yes | yes |
| RATE | no | no | yes |
+------+-----------------+-------------------+------+
'INDE' mode produces independent delay and rate solutions for
each IF while the other 3 modes produce a combined solution that
applies to all IFs. 'VLBA' mode differs from 'MK3 ' mode in
that multiband delay is assumed to be equal to single-band delay
in 'VLBA' mode but not in 'MK3 ' mode. Acceleration searches
may be requested independently of the mode setting.
BASELINE STACKING
BLING is capable of "stacking" data from different baselines.
This technique is explained in the Schwab and Cotton paper on
global fringe-fitting (Astron. J. vol. 88 p688, 1983) and is
also used in FRING. The basic idea is that the slope of the
summed visibility phase from baselines i-j and j-k with respect
to frequency is wholly determined by the residual delays of i
and k (since the delay at j cancels in the addition) and can
therefore be used to supplement the data from baseline i-k.
In the limiting case where there are N identical telescopes and
one which is much less sensitive this technique will reduce the
fringe-detection threshold by a factor of sqrt(N). BLING can
stack data that uses one intermediate antenna while FRING can
use up to two intermediate antennae. Allowing a second
intermediate antenna gives only a modest improvement over using
a single intermediate.
In reality neither BLING nor FRING average phases directly, as
suggested above, but sum a vector quantity with the phase of the
visibility data and an amplitude equal to the visibility weight.
This procedure is more appropriate to a process that uses a
Fourier transform (as both tasks do in their coarse searches)
but may break down if the source is not dominated by a bright
unresolved component. You may therefore need to disable
baseline stacking if you are observing a source with complex
structure and do not have a model that can be divided into
the data.
Stacking is enabled by default but will be disabled if you set
APARM(2) to a positive number.
BLING will use all of the possible intermediate antennae in the
data set, regardless of whether they are listed in the ANTENNAS
and BASELINE adverbs (which determine which baselines BLING will
search for fringes). If you wish to exclude an antenna from
the set of intermediates then you should use UVFLG to flag data
from that antenna and unflag the data after running BLING.
ACCELERATION SEARCHES
The acceleration search is carried out in a different way to the
searches in delay and rate. If an acceleration search is
carried out then BLING will try a number of coarse searches at
different acceleration values and pick the acceleration value
that gives the best degree of coherence as the starting point
for the fine search. This means that you must specify an
acceleration step size to use in the coarse search as well as
a search window. If the step size is zero or negative then
there will be no search in acceleration.
It should be obvious from the above that enabling acceleration
searches will slow the program down considerably. Since
enabling acceleration searches adds additional parameters to be
modelled, it will also tend to degrade the quality of your
solutions if you turn it on when it is not needed. You should,
therefore, restrict your use of acceleration searches to those
cases where it is absolutely necessary.
CONTROLLING BLING
The search windows and solution interval may be changed for
particular time ranges and baselines using a control file
specified as INFILE.
The control file should contain a number of baseline groups
Each group should start with a header card with the general
form
telescope1 telescope2 /
This informs BLING that the following records apply to baseline
telescope1-telescope2 where telescope1 and telescope2 are either
telescope names taken from the antenna table of the special name
"ANY". Thus
PT MK /
starts a group applying to the Pie Town - Mauna Kea baseline
while
PT ANY /
or
ANY PT /
starts a group applying to any baselines involving Pie Town and
ANY ANY /
starts a group applying to any baselines.
The header card should be followed by one or more cards having
14 fields. The fields are as follows.
1 integer Annual day number (Jan 1 = 1) of the day at which
the parameters on this line become valid.
2 time The time (hh:mm:ss - seconds are optional) at which
the parameters become valid.
3 integer Annual day number of the day on which the parameters
become invalid.
4 time The time at which the parameters become invalid.
5 real The solution interval for this time range.
6 real The multiband search window centre (nanoseconds).
7 real The multiband search window width (nanoseconds).
8 real The single-band search window centre (nanoseconds).
9 real The single-band search window width (nonoseconds).
10 real The rate window centre (mHz).
11 real The rate window width (mHz).
12 real The acceleration window centre (uHz/sec).
13 real The acceleration window width (uHz/sec).
14 real The acceleration search step (uHz/sec).
The group should end with a single slash ("/").
Here is an example baseline group.
PT MK /
27 12:00 27 13:00 10.0 0.0 100.0 0.0 100.0 0.0 20.0 0.0 0.0 0.0
27 13:00 27 14:00 5.0 0.0 100.0 0.0 150.0 0.0 30.0 0.0 0.0 0.0
/
The following rules apply.
* All of the windows must be defined in each card regardless
of whether the corresponding parameter will be solved for.
Of course, the values in the fields corresponding to unused
windows do not matter.
* More specific baseline groups override less specific ones
so that PT MK is preferred over PT ANY which is preferred
over ANY ANY for any given time.
* If there is no entry applicable to a given time for a
particular baseline then the solution interval will be set
from the SOLINT adverb and the windows will be set from the
DPARM adverb.
* If a delay or rate window is set to zero or a negative number
then BLING will search the full ambiguity range around the
given window centre.
* If the acceleration search step is zero or negative then there
will be no search in acceleration.
CHANGES FROM 15OCT96
* BLING now uses a simple interpolation scheme to refine the
fringe positions. This has allowed the default amount of
FFT padding to be reduced so that BLING is now much faster.
Consequently, errors listed in the BS table are now worst-case
errors and realistic errors will normally be a factor of 10 to
100 better for high SNR data.
CHANGES FROM 15JAN96
BLING has been extensively rewritten since the 15JAN96 release
of AIPS.
* You may now divide a model into the data.
* Baseline stacking is now possible.
* The logic for dividing the data into scans has changed. The
index file is no longer used to define solution intervals and
is no longer required. If an index file is present solution
intervals will be truncated to avoid crossing scan boundaries
defined by the index file but the scan will not be split into
equal subdivisions as before. [This change was made to support
the possibility of model division but also removes the need
to reindex the data for efficient file access.]
* Windows are now specified by a centre and width rather than
a beginning and an end. The format of the control file has
changed to reflect this. [This change makes BLING more
amenable to predictive window-setting.]
* The solution interval may now be changed for specific
baselines and times.
* Changes to the FFT set-up have improved the efficiency of
AP memory usage allowing more FFT interpolation to be used.
This has made it possible to remove the chi-squared fit
used to refine the fringe positions in previous versions
of BLING making the results more robust. The savings in
computer time have been swallowed by the increased sizes
of the FFTs, however.