Content-type: text/html Manpage of axcor

axcor

Section: User Commands (1)
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NAME

axcor - Apply special processing options to uv-data.  

PERSON RESPONSIBLE

mchw  

CATEGORIES

uv analysis  

DESCRIPTION

AXCOR is a MIRIAD task which applies special processing options to uv-data. By default, AXCOR applies the calibration files before it processes the uv-data into the output file. It was cloned from UVCAL.  

PARAMETERS

vis
The names of the input uv data sets. Multiple names can be given, separated by commas. At least one name must be given.
select
The normal uv selection commands. See the Users manual for details. The default is to process all data. Note that window selection can not be used with options=hanning, passband, contsub, or wide.
radec
Source right ascension and declination. These can be given in hh:mm:ss,dd:mm:ss format, or as decimal hours and decimal degrees. Setting RA and DEC will change the phase center to the RA and DEC specified. The default leaves the data unchanged.
options
This gives extra processing options. Several options can be given, each separated by commas. They may be abbreivated to the minimum needed to avoid ambiguity. Possible options are:
             unflagged visibilites.
             and imaginary parts of each spectral window.
             Exclude badchan and endchan specified below.
             by dividing the cross correlations by the 
             geometric mean of the autocorrelations.

             changes. This option also corrects the phase difference
             between the wide channels due to line length.
             options=linecal,avechan remakes the wideband from
             the channel data after the phase slope is removed. 
             where chi is the parallactic angle for Alt-Az antennas.
             Can be used when the source is strong. e.g. for
             planets. The passband is estimated from the lsb,
             smoothed within each spectral window, and applied
             to the lsb data. The complex conjugate is applied
             to the usb. This corrects for time variable IF
             passband errors. The uv-data must contain the same
             spectral windows in both sidebands of LO1.
 'uvrotate'  Rotate uv-coordinates from current to standard epoch.
             The standard epoch, ra, dec can be changed using PUTHD.
 'avechan'   Average unflagged spectral channels. Make new wideband.
            excluding badchan and endchan specified below.
 'slope'    Fit phase slope for each spectral window. Make new wideband.
            wideband phase is slope in units radians/GHz, and can
            be used to fit delay and antenna positions using BEE. 
            Exclude badchan and endchan.
 'holo'      
Enable other MIRIAD tasks to analyze interferometer pointing data. replace [u,v] with [dazim,delev] for ant1 in each baseline. if(dazim(ant1).eq.0 .and. delev(ant1).eq.0) then replace [u,v] with [dazim,delev] for ant2 in each baseline. If both ant1 and ant2 have zero dazim and delev, then [u,v] = [0,0]. [u,v] are in arcsec units. The data can be calibrated using select=uvnrange. N.B. not "uvrange". e.g. uvcal options=holo vis='infile' out='outfile'
   selfcal vis='outfile' 'select=uvnrange(0,1)' options=amp flux=1
Beam profiles can then be analysed using standard programs. e.g. UVPLT. Holography images of antenna surfaces are made using INVERT and IMHOL. INVERT makes a real image; options=imaginary makes the imaginary part. IMHOL combines the real and imaginary images into amplitude and phase images of the antenna surface. Related tasks: VARMAP makes images versus [dazim,delev] directly.

NOTE: Options=nochannel cannot be used with "hanning", "passband" and "contsub". For these 3 options no processing is performed on the wideband data.

badchan
Number of ranges of bad channels followed by list of up to 20 pairs of numbers giving range of channels to exclude in options=contsub and options=avechan. E.g. badchan=3,1,3,15,16,256,257 excludes the 3 ranges (1,3) (15,16) and (265,257)
endchan
Number of channels to drop from the ends of each spectral window in options=passband, contsub, and avechan. Default=0.
nave
Number of channels to average in options=passband. Default=1.
sigma
Rms noise level used to flag data in options=contsub. All channels are flagged if the rms noise level per channel is greater than sigma after subtracting the continuum. Endchan and badchan are not included in computing the rms. The default is sigma=0. which does not flag any data.
scale
Multiply the data and wideband by cmplx(scale1,scale2). Two values. Default is no scaling. If only one value is given it is assumed to be a real value. E.g. scale=0,1 multiplies the data by sqrt(-1)
offset
Subtract a complex valued offset from the uv-data. Two values give itude (after calibrations have been applied by uvcal) phase in degrees. Default is none.
model
Subtract a source model from the uv-data. Three values give the flux density [Jy], scale [nanosecs], and index for a radial power law:
        model = flux * (uvdist/scale) ** index
The model visibility is subtracted from the uv-data. Default model=0,0,0. i.e. no model is subtracted.
polcal
Subtract the source polarization from the uv-data. Two values give polarized intensity, Ip, and position angle, 2*psi, in degrees. Use same amplitude units as uv-data after calibration is applied.. subtract Ip*expi(2*psi)*expi(-2*chi) from LR, and subtract Ip*expi(-2*psi)*expi(2*chi) from RL where chi is the parallactic angle for Alt-Az antennas. Default=0,0. is no correction. After subtracting the source polarization, the averaged uv-data gives the instrumental polarization for each baseline.
polcode
Change the polarization code. Default polcode=0 makes no change. Polarizations are YX,XY,YY,XX,LR,RL,LL,RR,-,I,Q,U,V Polarization codes -8,-7,-6,-5,-4,-3,-2,-1,0,1,2,3,4 E.g. polcode=4 changes YX,XY,YY,XX to LR,RL,LL,RR E.g. polcode=-4 changes LR,RL,LL,RR to YX,XY,YY,XX
parot
Rotate uv coordinates and hence image by parot degrees. Rotation is +ve to the E from N. i.e. increasing PA. Default is no rotation.
seeing
Amplitude correction for atmospheric coherence, specified by the FWHM in arcsec, of a circular Gaussian fit to the phase calibrator(s) for the target source. Default seeing=0. is no amplitude correction.
axoff
Axis offset correction. Remove elevation dependent phase changes due to axis non-intersections. Inputs are AX1,AX2,AX3,AX4,... in nsec.
fcoff
Elevation dependent focus correction, assuming sin(el) dependence. Inputs are F1,F2,F3,.... in nsec
mltfile
Visibility scaling. Multiply data by amp*exp(i*pha). Inputs are Amp,Pha for all antennas.
out
The name of the output uv data set. No default.


 

Index

NAME
PERSON RESPONSIBLE
CATEGORIES
DESCRIPTION
PARAMETERS

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Time: 18:35:38 GMT, July 05, 2011