lband narrow gain curves sep01 thru 20aug02

written 25jun03

   The lband narrow cal values were measured on 28jan02 and installed on 11jul02. The calibration data (see aotm 99-02 sec 3.1) for 01sep01 through 20aug02  was  reprocessed with these new cal values. All of the sources with size less than 1 arcmin and gains between 6 and 12 K/Jy were then used to fit gain curves to the telescope az,za positions. The data was taken at 1300, 1375, 1415, and 1500 Mhz. There were 560 points at each frequency. The fits were done for the average of both polarization's (stokes I/2).
    The fits used was:

gain(az,za)=C0 + c1*za + c2*(za-14)^2 + c3*(za-14)^3 +
c4*cos(az) + c5*sin(az) + c6*cos(2az) + c7*sin(2az) + c8*cos(3az) + c9*sin(3az)
The (za-14) terms were only used for za GE 14 degrees. The plots show the fits for each of the 4 frequencies. Each plot is described below:
  • Figure 1 is the measured gain versus zenith angle (top) and gain versus azimuth angle (bottom). The sources about 0 degrees azimuth cover the north half of the dish while the sources about 180 degrees azimuth cover the southern half of the dish.
  • Figure 2 plots the gain versus azimuth and zenith angle. The length of the arrow is proportional to the gain (1 tick mark = 5 K/Jy). The angle of the arrow also measures the gain: vertical up is the maximum value, 90 degrees to the right is 25% of the maximum, and vertical down is 50% of the maximum value. Sources with declination < 18 deg (AO latitude) will appear on the upper half (northern part) of the dish. Sources with declination < 18 deg will appear on the lower (southern half) of the dish. Rising sources are on the left (west half of the dish) and set on the right  (east half of the dish).  The table at the bottom shows the average over the entire dish (9.42K/Jy) and the averages in 5 deg za steps.
  • Figure 3 shows the fit to the data. It is a 3rd order polynomial in za with the za^2, za^3 terms only being fit above za=14 deg. It also includes 1az,2az,3az sin and cosine terms.

  •     The top plot is (data - azfitComponents) vs za.
        The bottom plot is (data-zaFitcomponents-constant) vs az. The black line is the sum of the 1a,2az, and 3az terms.  The blue line is the sum of the 1az and 2az terms.
  • Figure 4 is the fit residuals (data -fit) versus azimuth and za. 1 tick mark is .5 K/Jy. The arrow direction is: up-->0 difference. right 90degrees data-fit = 1K/Jy, left 90 degrees data-fit=-1K/Jy.
  • Figure 5 is the (data - fit) by source.
  • The table below contains the fit values for comparison (the fit coef have more precision).
    (note that zap is (za-14))
    frq c0 za zap^2 zap^3 cosaz sinaz cos2az sin2az cos3az sin3az sig
    1300 10.42 -.080 3.5194e-02 -1.7028e-02 .04 .02 -.07 -.01 -.10 -.17 .59
    1375 10.75 -.083 1.6978e-02 -1.2664e-02 .09 -.05 -.09 .02 -.11 -.18 .51
    1415 10.36 -.085 2.9025e-02 -1.3854e-02 .07 -.05 -.13 0 -.14 -.19 .48
    1500 10.20 -.086 2.6364e-02 -1.2648e-02 .07 -.06 -.11 -.01 -.15 -.19 .49

        The absolute value of the gain fits rely on the lbn cal values and the fluxes of the sources. The gain curves can also be used as a transfer from the flux of the measured calibrators to the unknown flux of the users source. This will work independently of the cal values as long as they remain constant.

        To use the fits to gain, see the idl routines corhgainget (idl routines cor) and gainget (idl routines general).

    processing: x101/lb/lbnSep01_Aug02/