AIPS HELP file for ACFIT in 31DEC24
As of Fri Apr 19 1:22:59 2024
ACFIT: Task to determine antenna gains from autocorrelations
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 #
Data Selection
CALSOUR Sources to use to determine
gains.
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 select
SUBARRAY 0.0 1000.0 Subarray, 0=>1
ANTENNAS Antennas to select
Template file
IN2NAME Template UV file name (name)
IN2CLASS Template UV file name (class)
IN2SEQ 0.0 9999.0 Template UV file name (seq.#)
IN2DISK 0.0 9.0 Template UV file disk unit #
REFANT Reference antenna.
Control options
DOCALIB -1.0 101.0 > 0 calibrate data & weights
> 99 do NOT calibrate weights
GAINUSE CL (or SN) table to apply
FLAGVER Flag table version
SOLINT Solution interval
DOBAND If > 1 apply BP correction
BPVER BP table version to write
SMOOTH Smoothing function. See
HELP SMOOTH for details.
Does not apply to template
spectrum.
BCHAN 0.0 2048.0 Start channel for fit 0=>1
ECHAN 0.0 2048.0 Stop channel for fit 0=>all
APARM Control information:
(1) Polynomial degree for
source spectrum baseline
(2) Polynomial degree for
template spect. baseline
(3) Rpol sensitivity of
template antenna (Jy/K).
Use this if only one
polzn in data.
(4) Lpol sensitivity of
template antenna (Jy/K)
(5) Minimum allowed relative
gain value, 0 => 0
(6) Maximum allowed relative
gain value, 0 => all
(7) Maximum allowed relative
gain error, 0 => all
(8) Print level, 1=> print
gains.
(9) >0 => Baseline
independent fit.
(10)>0 => write out AC data
after baseline removed
BPARM Array of start and stop
channel numbers for baseline
fitting on source spectrum.
CPARM Array of start and stop
channel numbers for baseline
fitting on template spectrum.
XPARM Array of Rpol Tsys(IF) of
template scan. 0 => 1.0.
Use XPARM if only one polzn
in database.
YPARM Array of Lpol Tsys(IF) of
template scan. 0 => 1.0
SNVER -1.0 46655.0 Output SN table, 0=>new table
OUTNAME Output UV file name (name)
OUTCLASS Output UV file name (class)
OUTSEQ 0.0 9999.0 Output UV file name (seq. #)
OUTDISK 0.0 9.0 Output UV file disk unit #
BADDISK 0.0 9999.0 Disks to avoid for scratch
HELP SECTION
ACFIT
Task: To calibrate spectral line data using total-power spectra. The
method used is based on the 'template' spectrum method developed
for the calibration of spectral line VLBI data. You should
generate a 'template' spectrum, i.e. a high-quality spectrum from a
scan taken at a sensitive antenna at a reasonable elevation. Use
SPLIT and UVCOP to write this spectrum into a seperate uv-file.
ACFIT will then fit the template to all other total-power spectra
from all antennas (using a linear least-squares algorithm) and
generate an SN table which contains the relative gains of the
antennas as a function of time. These can be translated to absolute
gains simply by multiplication by the measured Tsys and Gain of the
template antenna.
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.
CALSOUR....List of sources to be used to determine gains.
All ' ' = all sources; a "-" before a source name.
means all except ANY source named. If the data
file is a single source file no source name need
be specified.
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 code:
' ' => 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 overide 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 selected. In order:
Start day, hour, min. sec,
end day, hour, min. sec. Days relative to ref.
date.
SUBARRAY...Subarray number to select. 0=>1.
ANTENNAS...A list of the antennas for which gains are
to be determined..
If any number is negative then all antennas listed
are NOT to be used and all others are.
The following specify the template spectrum file.
IN2NAME....Template UV file name (name). Standard defaults.
IN2CLASS...Template UV file name (class). Standard defaults.
IN2SEQ.....Template UV file name (seq. #). 0 -> highest.
IN2DISK....Disk drive # of template UV file. 0 => any.
REFANT.....Antenna to select from the template file whose
autocorrelation spectrum is to be used as the
template, useful if have multiple antennas in the
template file.
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).
The calibration is applied prior to the gain
determination.
GAINUSE....version number of the CL table to apply to
multisource files or the SN table for single
source files. 0 => highest.
FLAGVER....specifies the version of the flagging table to be
applied. 0 => highest numbered table.
<0 => no flagging to be applied.
SOLINT.....the interval (mins) over which to average the data
before solving for the gains. (0 => scan)
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......the version of the BP table to use. (0 => highest)
SMOOTH.....Specifies the type of spectral smoothing to be applied to
a uv database . The default is not to apply any smoothing.
The smoothing function is only applied to the spectra
from the main database, it is not applied to the template
spectrum. That should be smoothed by SPLIT if so desired.
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).
BCHAN......Start channel of region of spectrum to be used for
for fit, 0 => 1.
ECHAN......End channel of region of spectrum to be used for
for fit, 0 => all.
APARM......Task enrichment parameters.
(1) => degree of polynomial to be removed from
the source spectrum. The channel ranges over
which to determine polynomial baseline are
set by BPARMS.
(2) => Degree of polynomial to be removed from
the template spectrum. Channel range
specified in CPARM.
(3) => The gain of the RHC polzn of the template
antenna. (Jy/deg), 0 => 1.0
If only one polzn is present in the database
use APARM(3) to specify the antenna gain.
(4) => The gain of the LHC polzn of the template
antenna (Jy/deg), 0 => 1.0. Ignored if
only one polzn in data.
(5) => Minimum relative gain accepted (before
multiplication by Tsys and Jydeg. 0 => 0
(6) => Maximum relative gain accepted (before
multiplication by Tsys and Jydeg. 0 => all
(7) => Maximum percentage relative gain error
accepted, 0 => all. Recommend APARM(7)=20,
i.e. 20 percent
(8) => print level, 0 => hardly anything
1 => relative gain found for each antenna and
each averaging interval.
2 => gory details
(9) => Subtract baselines then fit gain => 0
Baseline-independent fit => 1.
If using a baseline-independent fit then
BCHAN and ECHAN should include channels
containing no emission.
(10) => If > 0 and APARM(9)=0 then will write out
the total power spectra with spectral
baselines removed to an output file
given by OUTNAME etc.
BPARM......Array of start and stop channels to use for
fitting a polynomial to any residual spectral
baseline. Order of polynomial is given by
APARM(1). If all 0, no residual baseline will be
removed.
CPARM......Same as BPARM but used for the template spectrum
Order of polynomial is given by APARM(1). If all
0, no residual baseline will be
removed.
XPARM......Array of RHC Tsys(IF)(K) - system's temperature of
the template scan for different IFs. 0 => 1.0.
If only one polzn in the database use XPARM to
specify the Tsys values.
YPARM......Array of LHC Tsys(IF)(K) - system's temperature of
the template scan for different IFs. 0 => 1.0.
If only one polzn in the database then YPARM
will be ignored.
OUTNAME....Output UV file name (name). Standard defaults.
OUTCLASS...Output UV file name (class). Standard defaults.
OUTSEQ.....Output UV file name (seq. #). 0 => highest.
OUTDISK....Drive # of output UV file. 0 => highest with
space for the file.
BADDISK....A list of disks on which scratch files are not to
be placed. This will not affect the output file.
EXPLAIN SECTION