AIPS HELP file for BPCOR in 31DEC24
As of Thu Apr 18 20:02:07 2024
BPCOR: Task to apply various corrections to BP spectra.
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.
STOKES Stokes type to process
FREQID -1.0 9999.0 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 => 1.
BPVER 1.0 9999.0 Input BP table version
(will append new table)
CODETYPE Components to smooth 'R&I',
'A&P','A','P',' ' => 'R&I'
Not used for OPCODE='SPEC'
OPCODE Correction mode:
'FUNC' => scale by function
'HANN' => Hanning smooth
'BOXC' => Boxcar smooth
'GAUS' => Guassian smooth
'SINC' => Sinc smooth
'BMED' => Broadened median
filter
'SPEC' => spectral index
correction
' ' => pass BP table
obeying BPARMS
APARM Parameters (see HELP BPCOR).
For smoothing then:
APARM(1) = smoothing function
diameter (channels)
HANN, BOXC - full diam
GAUS - FWHM
SINC - first nulls
BMED - median window diam
APARM(2) = smoothing support
func diameter in chans.
For spectral index (SPEC)
APARM(1) = spectral index
APARM(2) = start channel
APARM(3) = end channel
APARM(4) = channel about
which spectrum will
pivot
For interpolation (POLY)
APARM(1) = polyn. order to
fit to amplitude
APARM(2) = polyn. order to
fit to phase
BPARM Parameters (see HELP BPCOR)
(1) 1=> set phase to zero
(2) 0=> normalise BP ampl
(3) first channel in
normalization
(4) last channel in norm.
CPARM Channels to fit
(OPCODE = 'POLY' only)
Pairs of starting, ending
channels to use in the fit
CALIN
Text file for FUNC mode
BADDISK 0.0 9999.0 Disks to aviod for scratch
HELP SECTION
BPCOR
Task: Task to correct bandpass correction tables.
Use: BPCOR applies various smoothing and other correction methods to
the selected data in the input BP table. All other data in the
table are copied to the output table unmodified. The output BP
table is always version number one higher than the previous
highest number.
FUNCTION:
The calibration source may not have a frequency-independent
flux because of, for example, absorption due to hydrogen in the
Galaxy. The FUNC mode may be used to correct the amplitude of
the BP for an arbitrary spectral shape. The user provides the
shape, listing the channels to be corrected and their correction
factors in a text file.
SMOOTHING:
The principal correction mode is smoothing: several smoothing
methods are available including Hanning, Gaussian, Boxcar and
Sinc smoothing. Broadened median window filtering is also
possible. To avoid spectral shifts, all smoothing functions are
applied symmetrically. Boxcar of width "2" actually does 3
channels averaging, for example, channels 9, 10, and 11 for
output channel 10. Width 3 does the same. Width 4 is needed to
include channels 8 and 12. This is different than boxcar with
SMOOTH.
SPECTRAL INDEX CORRECTION:
The BP spectra can also be corrected for the effects of a
spectral index across the band. Note that BPASS has a more
extensive spectral index option and handles BP normalization
as well.
INTERPOLATION:
The BP spectra can also be interpolated with a polynomial
(OPCODE = 'POLY') NOT IMPLEMENTED!!
The corrected complex bandpasses can be normalised before output
and the phase response can be set to zero if desired.
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.
STOKES.....The desired Stokes type to select:
'R ', 'L ', 'RL', ' '=> 'RL'.
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.
EIF........Highest IF to process. 0=>all higher than BIF
TIMERANG...Time range of the data to be used. In order:
Start day, hour, min. sec,
end day, hour, min. sec. Days relative to ref.
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. Do only one at a time.
BPVER......The input BP table version number. NOTE: There
is NO default value. The output BP table will
always be version 0 (i.e. appended after the
last existing BP table).
CODETYPE...Which components are to be smoothed.
'R&I'=> real and imag; 'A&P'=> ampl and phase,
' '=> 'R&I'
'A ' or 'P ' - used for opcode 'POLY' only
This parameter is ignored for OPCODE = 'SPEC'
OPCODE.....Type of correction to be performed:
'FUNC' - input gain function
'HANN' - Hanning smoothing
'BOXC' - Boxcar smoothing
'GAUS' - Gaussian smoothing
'SINC' - Sin x/x smoothing.
'BMED' - Broadened median window filtering.
'SPEC' - Spectral index correction.
'POLY' - polynomial interpolation - NOT IMPLEMENTED
APARM......Smoothing parameters:
APARM(1) = Smoothing function diameter (chan)
'HANN','BOXC' - full width.
'GAUS' - FWHM
'SINC' - width between first nulls.
'BMED' - median window diameter.
'SPEC' - spectral index present in
the data, defined as
S = So * freq ** alpha.
This spectral index will be
removed from the data.
'POLY' - order of polynomial to fit
to amplitude
APARM(2) = Smoothing function support (chan)
(not required for OPCODE='BMED').
'SPEC' - start channel for spectral
index correction.
'POLY' - order of polynomial to fit
to phase
APARM(3) 'SPEC' - stop channel for spectral
index correction.
APARM(4) 'SPEC' - channel about which the
the spectrum will pivot.
If zero will be the central
channel.
BPARM......Options after correction is completed.
BPARM(1): 0=> phase unchanged;
1=> set phase to zero across the band;
BPARM(2): 0=> normalise the bandpass amplitude;
1=> bandpass amplitude unchanged;
BPARM(3): first channel to use in normalization
0 -> N/8 + 1
BPARM(4): last channel to use in normalization
0 -> N - N/8
CPARM......Channel to use in the interpolation.
(OPCODE = 'POLY' only)
CPARM(1): starting channel for window 1
CPARM(2): last channel for window 1
etc. for a total of 5 windows
CALIN......Name for input text file used in the FUNC mode. e.g.
CALIN='MYAREA:MYFILE.TXT'. Each line of the file is used
to give the correction factor (actually divisor) for one
channel. Thus, a weak absorption feature would be
corrected with
63 0.999
64 0.995
65 0.990
66 0.988
67 0.991
68 0.996
where channels 1-62 and 69-n have no correction applied.
Blank lines or ones beggining with a $ or an * are ignored.
Others may cause problems.
BADDISK....A list of disks on which scratch files are not to
be placed. This will not affect the output file.
EXPLAIN SECTION