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 # BIF IF number; 0 => 1 BCHAN Channel number; 0 => 1 STOKES Stokes parameter; Recognized values are: 'RR ', 'LL ' ANTENNAS The well calibrated antennas whose gains are forced to 1 and not corrected SNVER SN table number; <0 => SN table is not made 0 => highest OUTTEXT Name of the file to write the crossings and ampl. ratios APARM Control parameters APARM(1) UVRADX in megalamda; 0 => 0.5 APARM(2) UVRADY in megalamda; 0 => 0.5 APARM(3) 0 => rect. area; 1 => elliptical area APARM(4) 0 => no print 1 => print results on screen

UVCRS Task: This task finds the crossing points of UV-ellipses, calculates the average ratios of the amplitudes at the crossing points and finds the solution for the gains of antennas by a least squares approach minimizing the deviation of the ratios from 1 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. BIF........IF number; 0 => 1 BCHAN......Channel number; 0 => 1 STOKES.....Stokes type. Recognized values are: 'RR ', 'LL ' ANTENNAS...The numbers of well calibrated antennas whose gains are forced to 1 and not corrected SNVER......SN table number; <0 => SN table is not made; 0 => highest; OUTTEXT....Name of the file in which to write the crossing points and ratios. Standard form, e.g 'MYAREA:OUT' where OUT is the name of the file to be created, and MYAREA is an environment variable defined before starting up AIPS. APARM......Control parameters APARM(1)...UVRADX at megalamda; 0 => 0.5 APARM(2)...UVRADY at megalamda; 0 => 0.5 APARM(3)...Type of crossings region; 0 => rectangular; 1 => ellipse APARM(4)...To print or not some intermidiate results on the screen; 0 => no print; 1 => print

The program finds all crossings points of UV-ellipses. The two points from two UV-ellipses are defined as 'crossing' if the vector connecting them is located inside a given region. The region can be rectangular or elliptical. The type of the region and its size are determined by the input parameters APARM. The logarithm of a ratio of an amplitude of a given point and the amplitudes of all 'crossing' points of a neighbouring UV ellipse is calculated. Then the average logarithm of the ratios for a given point is constructed. Finally all these logarithms for all crossingspoint of a given UV-ellipse are averaged. This final average logarithm of the amplitude ratio is associated with the given pair of baselines. The logarithm of the amplitude ratios is preferable than the ratios themselves for several reasons: 1..We have to consider the ratios 0.1 and 10 to be equally bad rather than 0.1 and 1.9 2..Averaging of logarithms (for ratios close to 1) is equivalent to averaging of deviations of the ratios from 1. 3..Averaging of logarithm excludes the ambiguity occuring when we are using the reciprocals of ratios. For example 0.5(1 + 3)=2. But 0.5(1/1 + 1/3)=2/3; And 1/2 is not equal 2/3. The same example when averaging logarithms: 0.5(log(1)+log(3))=0.5log(3); average ratio = exp(0.5log(3))= sqrt(3); reciprocal case: 0.5(log(1)-log(3))=-0.5log(3); average ratio = exp(-0.5log(3))=1/sqrt(3); 4..The use of logarithms produces a linear system of equations connecting logarithms of antennas gains and ratios. So we can use a linear least square method to determine the solution for the antennas gains minimizing the deviation of the ratios from 1. The program prints the results in the OUTTEXT. The sign '?' before a ratios lines indicates the case of too large a deviation of the ratios from 1 (RATIO > 2; or RATIO < 0.5). The second column's integer indicates the number of crossings that occured for a given pair of baselines. The last two columns in the table represent the original ratios and the ratios after applying the solution found for the antennas gains. If you desire to use the solution for different IFs and different polarizations you have to run the program for the first IF and polarization from your list with 'snver'=0 and then repeat the program in consecutive order for all the polarizations and IFs in your data using the same number of 'snver'. Limitations 1.Number of visibilities less than 50000. 2.Duration of an experiment has to be less than 24 hours