AIPS HELP file for DFTIM in 31DEC22
As of Tue Jun 6 3:07:10 2023
DFTIM: Images the DFT of an arbitrary point using UV data
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 #
OUTNAME Output MA file name (name)
OUTCLASS Output MA file name (class)
OUTSEQ 0.0 9999.0 Output MA file name (seq. #)
OUTDISK 0.0 9.0 Output MA file disk unit #
UVRANGE 0.0 Range of projected spacings
(thousands of wavelengths)
TIMERANG Time range to select:
Start Day, Hour, Min, Sec
End Day, Hour, Min, Sec
SHIFT Shift in asec at ref position
STOKES I, Q, U, V, RR, LL, VV, HH
BPARM Control parameters
2 : averaging interval (sec)
3 > 0 -> write error image
SOURCES Source name
QUAL -10.0 Calibrator qualifier -1=>all
CALCODE Calibrator code ' '=>all
SELBAND Bandwidth to select (kHz)
SELFREQ Frequency to select (MHz)
FREQID 0.0 Frequency ID number: 0 -> 1
SUBARRAY 0.0 1000.0 Sub-array, 0=>all
BIF 0.0 First IF to include
EIF 0.0 Last IF to include
BCHAN 0.0 First channel to include
ECHAN 0.0 Last channel to include
NCHAV 0.0 Number channels to average
DOCALIB -1.0 101.0 > 0 calibrate data & weights
> 99 do NOT calibrate weights
GAINUSE CL (or SN) table to apply
DOPOL -1.0 10.0 If >0.5 correct polarization.
PDVER PD table to apply (DOPOL>0)
BLVER BL table to apply.
FLAGVER Flag table version
DOBAND -1.0 10.0 If >0.5 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.
BADDISK Disks to avoid for scratch
Use: Makes an image of the DFT of the complex visibilities found in a
UV data base for an arbitrary point in the sky as a function of
time and frequency. Note that the visibilies are shifted under
control of SHIFT and then the real parts are simply summed over
all baselines in each time and spectral interval. Task ACIMG
makes this "waterfall" image for auto-correlation data. Task
TBAVG makes a UV data set of the summed visibilities while DFTPL
makes a plot of a selected frequency range.
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.
OUTNAME....Output name of image(name). Standard defaults.
OUTCLASS...Output name of image(class). Standard defaults.
OUTSEQ.....Output name of image(seq. #). 0 => highest unique
OUTDISK....Disk drive # of Output image. 0 => highest with space
UVRANGE....Range (min, max) of projected baselines to include
0,0 => all baselines
TIMERANG...Time range of the data to be plotted. In order:
Start day, hour, min, sec, End day, hour, min, sec.
Days relative to reference date. 0 => full range.
SHIFT......Shift in arcseconds - the data are shifted, summed, and
then plotted. These are shifts in arc seconds at the
reference point -
RA = RA0 + SHIFT(1)/cos(DEC0), DEC = DEC0 + SHIFT(2)
STOKES.....Only one Hermitian polarization is allowed: I, Q, U, V,
RR, LL, VV, HH. Cross-hands do not have the Hermitian
property and so are not allowed.
2 = averaging interval in seconds (0 => 60)
NOTE: an interval beginning at a sample time T1 will include
all samples < T1+BPARM(2). If your data occur at 5 second
intervals and you want no averaging, set BPARM(2) < 5. If
you want to average pairs of samples, set 5 < BPARM(2) < 10.
3 = > 0 -> write also an error image
SOURCES....Source to be copied. ' '=> all; if any starts with a
'-' then all except ANY source named.
NOTE: this task makes sense only if you select a single
QUAL.......Qualifier of source to be processed. -1 => all.
CALCODE....Calibrator code of source to be processed. ' '=> all.
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
override that of FREQID. However, setting SELBAND and
SELFREQ may result in an ambiguity. In that case, the task
will request that you use FREQID.
SUBARRAY...Sub-array number to process. 0=>all (okay if not
BIF........Start IF; 0 -> 1
EIF........End IF; 0 -> max
BCHAN......Start channel; 0 -> 1
ECHAN......End channel; 0 -> max
NCHAV......Number of channels to average. Note that ECHAN is
adjusted if necessary to make (ECHAN-BCHAN+1) and integer
multiple of NCHAV. 0 -> 1.
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 multi-source
files or the SN table for single source files.
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 apply. <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
(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
IMAGR uses DOBAND as the nearest integer; 0.1 is therefore
BPVER......Specifies the version of the BP table to be applied
0 => highest numbered table.
<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
BADDISK....The disk numbers to avoid for scratch files (sorting
DFTIM: Makes image of DFT at arbitrary point showing time vs frequency
RELATED PROGRAMS: TKPL, LWPLA, TVPL
DFTPL was written primarily to assist stellar observers
interested in time variable phenomena (e.g., outbursts on RS CVn's,
dMe flare stars, etc.). Since these stars are in general unresolved,
it's often pointless to make a synthesis map for each time interval.
Instead one can do the following: 1) make a large field map using the
entire XY sorted data base and identify all background sources; 2) run
APCLN or IMAGR with boxes around these sources (but not the stellar
source of interest) and CLEAN them down to the noise; 3) using the
resulting CLEAN components as a model of the background sources, use
UVSUB to subtract the model from the UV data base; 4) use UVSRT to
sort the data into TB order.
If NO confusing sources of any importance can be found in the
field, then of course steps 1-4 can be skipped and one simply begins
with a TB sorted (calibated and edited) data base. he UV data base on
an EXPORT tape is sorted in TB order, but one might have to use the
verb PUTHEAD to indicate this fact in the header. This is done by
first setting KEYWORD to 'SORT' and KEYSTRING to 'TB' and typing PUTH.
The task DFTPL allows one to plot the direct fourier transform
of the measured visibilities as a function of time for an arbitrary
shift in RA and DEC. It will plot either points, points with error
bars, or histogram format. The averaging interval is adjustable
(BPARM(2)). The data time segment may be specified (through APARM).
The task runs somewhat faster than UVPLT. Hence one can moniter all
Stoke's parameters of a star with time VERY quickly, without having to
resort to generating a tedious sucession of maps.