OUTNAME Save beam images if not blank OUTSEQ 0.0 9999.0 Output files name (seq. #) OUTDISK Output files disk unit # INFILE First input data file IN2FILE Second input data file OUTTEXT Output file to record the fitted parameters VPARM 1. Fractional power cutoff for fit 0 => 0.05 (5 percent of peak) 2. Antenna diameter, meters 0 => 25 3. number of iterations for nonlinear least square fit 0 => 4 4. Degree of the fit polynom. 0 => 3 5. exclude data with |phase| > APARM(5) degrees 0 => The cutoff = 60 deg. -1 =>do not exclude points on the basis of phase 6. 0 => combine the two input files (Stokes 'I') 1 => Fit model to each input file separately and write out differences (squint) 7. 0 => do not change the input files 1 => switch the first two columns of the input files 8. > 0 -> Complex normalize else normalize by peak amp 9. width factor to convolve to grid 0 -> 1.4, smaller is smoother, wider 10. > 0 Do not normalize the fit parameters 11. > 0 => data are power not voltage BPARM These are used to simulate data for testing the program. 1. Coefficient of the first degree term (G1) 0 => -0.1 2. Coefficient of the second degree term (G2) 0 => 0.0034 3. Coefficient of the third degree term (G3) 0 => -4.60E-05 4. XSHIFT - horizontal beam offset 0 => 0.1 arc minutes 5. YSHIFT - vertical beam offset 0 => 0.05 arc minutes 6. eccentricity 0 => 0.1 7. Error of eccent. guess 0 => 0 8. Major axis position angle, deg. 0 => 60 9. Error of position angle guess, degrees 0 => 5 DOPLOT 1,3,5,7 -> make contour plots 2,3,6,7 -> make IRING plots 4,5,6,7 -> make IRING difference plots OPTYPE ' ' => observed data used, eccentricity and Pos. angle are not fitted 'ELLI' => observed data used, eccentricity and Pos. angle are fitted. 'SIMU' => simulated data are used; eccentricity and Pos. angle are fitted. PRTLEV 0 => print the polynomial coefficients and errors. 1 => print observed data and fitted values as well. X,Y coordinates use 2 => print observed data and fitted values as well. RO, PHI coordinates use Header is not printed DOTV -1.0 1.0 > 0 Do plot on the TV, else make a plot file GRCHAN 0.0 8.0 Graphics channel 0 => 1. BADDISK 0.0 9999.0 Disks to avoid for scratch

PBEAM Type: Task Use: Fits an analytic function to raster scan beam data. It can also make contour plots of the data, the fit model, and the residual (data-model) and can output interpolated images of them. In addition, it can make plots of the data and model in rings about the fit center (ring-by-ring and sum interior to ring) and plots of the same rings in the residual image. Adverbs: OUTNAME....Output image file name (name). If not blank, output images will be made of the data, model, and residual. If DOTV <= 0, OUTNAME must be set and the initial plots of the image will be attached to the image files. If OUTNAME is blank, DOTV will be forced to true. OUTSEQ.....Output UV file name (seq. #). 0 => highest. OUTDISK....Disk drive # of output UV file. 0 => any. INFILE.....Input file with the raster scanned beam data for one polarization. The accepted format is that used by UVHOL. Lines starting with '#!' are headers, and contain a variety of information. The lines beginning '#! RefAnt' are particularly inportant and should not be altered from those provided by UVHOL. The give reference antenna, antenna number, Stokes and frequency for the following beam data. The data lines have a free format giving X, Y, Amplitude, and Phase. IN2FILE....Input file with beam data for the 2nd stokes (optional). OUTTEXT....Output file to record the fitted parameters and data. VPARM..... 1. Minimum normalized power level used. 0 => 0.05 (5 percent) 2. Diameter of antenna, meters. 0 => 25 3. number of iterations for nonlinear least square. 0 => 4 4. Degree of the fitted polynomial. 0 => 3 5. Exclude points with abs(phase) > VPARM(5) degrees 0 => The cutoff is equal 60 degrees .LE. 0 => do not exclude points on the basis of phase 6. 0 => combine the two input files and fit to Stokes 'I' 1 => Fit the model to both input files separately, and compute the beam squint parameters. The INFILE data define the reference position. 7. PBEAM expects the first column of the input files to be the horizontal offset and the second to be the vertical offset. If your data file has the opposite convention, set VPARM(7)=1 to switch the columns before fitting. 8. The incoming data are normalized by the value of the peak amplitude. This can be done in a complex fashion using the amp and phase at the peak iff VPARM(8) > 0. 9. The images are constructed by smoothing to a grid with a circular Gaussian function. The width of that function is controlled by VPARM(9) with default 1.4. Larger values mean that the data samples do not smooth together and so by 2.0 the image is rather "boxy" around each sample. Smaller values smooth the image further but also fatten the beam. This does not affect the fit results, only the displays. 10. The beam fit parameters are usually normalized so the G0 parameter has value 1.0. To omit this normalization, set VPARM(10) > 0. 11. When the UVHOL output is for one moving and one fixed antenna, then the values are effectively voltages and must be squared to fit the beam. However, when both antennas are moving, then the values are visibilities or power and the data should not be squared. Set VPARM(11) > 0 to indicate this case. BPARM......Beam simulation parameters. 1. Coefficient of G1, the first degree term; 0 => -0.1 2. Coefficient of G2, the second degree term; 0 => 0.0034 3. Coefficient of G3, the third degree term; 0 => -4.60E-05 4. XSHIFT; 0 => 0.1 (Beam offset in azimuth) 5. YSHIFT; 0 => 0.05 (Beam offset in elevation) 6. Eccentricity; 0 => 0.1 7. Error of the eccentricity's guess 8. Position angle, degrees; 0 => 60 9. Error of the position angle guess, degrees; 0 => 5 G0 is fixed at 1.0. DOPLOT.....Controls whether plots are done: DOPLOT = 1,3,5,7 -> make contour plots of each image (data, model, residual) DOPLOT = 2,3,6,7 -> make IRING-like plots comparing data and model with average beam in ring and sum of beam values inside ring DOPLOT = 4,5,6,7 -> make plots of the IRING-like average in each ring and sum interior from the difference image and of the difference IRING divided by the model IRING. OPTYPE.....' ' => the given number of the polynom's coefficients, and the X-, Y-shifts are fitted to the data 'ELLI' => the given number of the polynom's coefficients, the X-, Y-shifts, eccentricity and position angle are fitted to the observed data 'SIMU' => the given number of the polynom's coefficients, the X-, Y-shifts, eccentricity and position angle are fitted to the simulated data The position angle is defined as the angle between the the major axis and the Y (elevation) axis. A positive angle is defined as the rotation which turns the positive X axis into the positive Y axis. PRTLEV.....0 => print only the coefficients and errors of the fit. 1 => print observed and fitted data X,Y coordinates use 2 => print observed and fitted data RO, PHI coordinates use Header is not printed DOTV.......> 0 Do plot on the TV. GRCHAN.....Graphics channel 0 => use channels 1,2,3,4 which allows color to separate things being plotted. Labels go in 1 (usually yellow), contours and the IRING connecting line go in 2 (usually green), data IRING X's go in 4 (usually cyan), and model IRING plus signs go in 3 (usually pink). BADDISK....A list of disks on which scratch files are not to be placed. This will not affect the output file.

PBEAM: Fits for the coefficients of an analytical model to raster-scanned data produced by UVHOL. Documentors: L.R. Kogan, R.A. Perley The program fits a polynomial of the form: GO + G1*ARG + G2*(ARG^2) + G3*(ARG^3) + ... where ARG = (X1*EC)^2 + Y1^2 X1 = (X-X0)*COS(PHI) + (Y-Y0)*SIN(PHI) Y1 = -(X-X0)*SIN(PHI) + (Y-Y0)*COS(PHI) X0 and Y0 are offsets from the fiducial center. EC = b/a is eccentricity of the ellipse PHI is position angle of the major axis In the case of circular beam (EC and PHI are not fitted) the fit polynomial looks simpler: GO + G1*ARG + G2*(ARG^2) + G3*(ARG^3) + ... where ARG = (X-X0)^2 + (Y-Y0)^2 X0 and Y0 are offsets from the fiducial center. The order of the polynomial is specified by the user via VPARM(4). Non linear least square method is used for the fitting. The number of iterations in the non linear least square fitting is specified by the user via VPARM(3). The default for VPARM(3)=4 and VPARM(4)=3 works fine in most cases. The task reads from external files produced, for example, by the AIPS task UVHOL. UVHOL processes VLA holography data produced by the VLA's online holography programs. PBEAM assumes, but does not require, calibrated data. Normally, this means the maximum amplitude is 1.0, and the phase is zero. PBEAM searches for the maximum amplitude in the raster data, and normalizes all measurements by this value. (This is necessary because large pointing errors will throw off the amplitude calibration). The phase is used to discriminate against data taken in the first sidelobe This test can be turned off by setting VPARM(5)=1. After normalizing the amplitude, PBEAM squares the amplitudes and applies a cutoff given by VPARM(1). High sidelobe data are rejected via the phase test, if desired. The requested model is then applied to the surviving data. If the model is to be applied to only a single polarization, IN2FILE must be left blank. Both circular polarizations may be processed simultaneously if they are specified via INFILE and IN2FILE. Although it is not necessary for these data to be on the same grid, the only points which will be utilized in the analysis will be those which are taken at very similar grid points. There are two distinct modes available when both polarizations are provided: If VPARM(6) = 0, the input files are vector averaged (normally producing a Stokes' I value) and the model applied. The X and Y offsets found then represent the pointing error of the antenna. If VPARM(6) = 1, the two input files are separately analyzed (producing offsets for the two polarizations separately). The program then takes the difference in each axis, and writes out the beam squint amplitude and position angle. The sign of the offsets is such that a positive XSHIFT means the antenna beam is located at a greater azimuth than the reference position. A positive YSHIFT means the antenna beam is at a higher elevation than the reference position. The squint angle (PHISHIFT) is the p.a. of the IN2FILE beam's maximum w.r.t. the INFILE beam maximum, with the horizontal axis defining the zero, and a CCW direction defined as positive. The units of XSHIFT, YSHIFT, and ROSHIFT (squint separation) are in arc minutes. Error estimates, derived from the errors in the R and L beam centers, of the squint parameters are produced and printed. The program first divides the data by a rough estimate of the beam maximum. The analytic model described above is then fitted. The coefficients are then divided by G0 (the fitted beam maximum) and printed. Error estimates are also given, after normalization by the value of G0. The post-fit RMS is printed. VPARM(5) is a phase cutoff, intended to prohibit high sidelobe values from entering the analysis. Only use this if the data are calibrated (so the main-beam values are near 0 degrees). The BPARMs are used for generating fake beam data, for testing the program. This option is enabled when OPTYPE = 'SIMU'. The program will produce PL files, showing the input data and the fitted curves. The program will fit for beam ellipticity by setting OPTYPE = 'ELLI'. It is advised to use a high power cutoff (say, 40 percent) to avoid skewing the results by the quadrupod structures. PBEAM can work with several reference antennas but only with one investigared antenna. So the input file should include data only for one antenna. Three images are written when OUTNAME is not blank - the data, the model, and the residual (data-model). They are accompanied by plot files if DOTV <= 0. If OUTNAME is blank or DOTV > 0, the plots are displayed on the TV. The plots are contour images with LEVS from -0.95 to +0.95 in steps of 0.1 for the data and model images and from -0.145 to +0.145 in steps of 0.01 for the residual image. The plots also put little plus signs where the data samples actually occurred.