AIPS HELP file for FIXAL in 31DEC24
As of Wed Nov 13 7:18:04 2024
FIXAL: Least squares fit aliasing function and remove
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 names for line sources
NO '-' usage
CALSOUR Continuum source names
FLAGVER Flag table version
IN2NAME Input cal file name (name)
IN2CLASS Input cal file name (class)
IN2SEQ 0.0 9999.0 Input cal file name (seq #)
IN2DISK 0.0 9.0 Input cal file disk unit #
BDROP 1.0 512.0 start chan in cal for cont
EDROP 1.0 512.0 end chan in cal for cont
OUTNAME Output UV file name (name)
OUTCLASS Output UV file name (class)
OUTSEQ -1.0 9999.0 Output UV file name (seq. #)
OUTDISK 0.0 9.0 Output UV file disk unit #.
BCHAN Lowest channel for cals
ECHAN Highest channel for cals
ICHANSEL Select channels to fit: NOTE
this is start,end,increment
and IF for each region
DPARM -1.0 1.0 <=0 => average polarizations,
IFs, times, antennas
(5) > 0 keep imaginary
(6) > Hanning smooth
FLUX 0.0 Flag data if residual flux in
any fit channel is > FLUX
0 -> 10**20
CUTOFF 0.0 Flag data if RMS of residual
in fit channels > CUTOFF
0 -> 10**20
BADDISK Disks to avoid for scratch
HELP SECTION
FIXAL
Task: EXPERIMENTAL TASK!
This task does a special spectral fit designed to correct for
aliasing of the continuum into the observing band caused only
for EVLA-EVLA baselines when observed in the VLA-EVLA
transition with the old correlator.
The process which one must undertake to correct data affected
by this problem is:
1. Flag EVLA-EVLA baselines in the FG table
2. Run BPASS on the VLA-VLA and VLA-EVLA baselines
3. Undo the EVLA-EVLA baseline flagging in the FG table
4. Run SPLAT to apply the BP table
5. Run UVAVG on one or more calibrator scans to make scan
average data for the "cal"
6. Run FIXAL applying the cals of step 5. It reads in the data
averaging each baseline.pol/IF separately. Sums up the cal
channels BDROP through EDROP and divides the cal by this
complex average. Then it fits the normalized cal to the
channels of the input data to get the continuum flux and
subtracts the channel-dependent part of that from the data.
A procedure, FXALIAS, has been written to help implement this
process.
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....Sources to be baselined using the specified ICHANSEL.
' '=> all except those in CALSOUR. The '-name' usage is
not allowed here.
CALSOUR....Sources to be baselined using BCHAN-ECHAN rather than
ICHANSEL. ' ' => none.
FLAGVER....specifies the version of the flagging table to be applied.
0 => highest numbered table.
<0 => no flagging to be applied.
IN2NAME....Input cal file name (name). Standard defaults.
IN2CLASS...Input cal file name (class). Standard defaults.
IN2SEQ.....Input cal file name (seq. #). 0 => highest.
IN2DISK....Disk drive # of input cal file. 0 => any.
BDROP......Begin channel for cal file unaffected by aliasing
NO DEFAULT
EDROP......End channel for cal file unaffected by aliasing
NO DEFAULT
OUTNAME....Output UV file name (name). Standard defaults.
OUTCLASS...Output UV file name (class). Standard defaults.
OUTSEQ.....Output UV file name (seq. #). 0 => highest unique
OUTDISK....Disk drive # of output UV file. 0 => highest with
space for the file.
BCHAN......Lowest channel number in the input file to fit CALSOUR
sources. 0=> Nchan/8
ECHAN......Highest channel number in the input file to fit CALSOUR
sources. 0=> Nchan - Nchan/8
ICHANSEL...For sources named in SOURCES, selects up to 20 groups of
channels/IF(s) to fit as sets of (Start,end,inc,IF),
i.e., ICHANSEL = 6,37,1,0, 92,123,1,0 for two regions
applying to all IFs. The first group for which
ICHANSEL(2,i) <= 0 ends the list. Defaults: Any IF having
no group assigned to it, gets a group including all
channels. ICHANSEL(1,j) defaults to 1,
0 < ICHANSEL(2,j) < ICHANSEL(1,j) defaults to Nchan.
ICHANSEL(3,j) < 1 or > ICHANSEL(2,j)-ICHANSEL(1,j)+1
defaults to 1.
ICHANSEL(4) <= 0 => this group applies to all IFs.
DPARM......(1) > 0 => do NOT average polarizations in fitting the
aliasing function
(2) > 0 => do NOT average IFs in fitting the aliasing
function
(3) > 0 => do NOT average times in fitting the aliasing
function
(4) > 0 => do NOT average antennas in fitting the
aliasing function
(5) > 0 => do full complex aliasing function
< 0 => zero the imaginary part of aliasing function
(6) > 0 => Hanning smooth the aliasing function
FLUX.......If the residual flux in any channel used to fit the
baseline exceeds FLUX, then the spectrum for that time, IF,
and polarization is fully flagged. <= 0 => 1.0E20
CUTOFF.....If the RMS flux in the channels used to fit the baseline
exceeds CUTOFF, then the spectrum for that time, IF, and
polarization is fully flagged. <= 0 => 1.0E20
BADDISK....The disk numbers to avoid for scratch files (sorting
tables mostly).
EXPLAIN SECTION