Pitch, roll, focus corrections at cband after SE quadrant adjusted.

july,2001

     The adjustments to the panels in the SE quadrant of the dish were completed at the beginning of jul01. On 27jun01 4 sources were tracked using the cband system at 4500, 4860, 5000, and 5400 Mhz. The standard "heiles" pattern was used to measure the beam parameters. The sources tracked were:
 
source
flux at 4860
J0735+331
.84 Jy
J0827+293
.73 Jy
J0901+290
.94 Jy
J1143+221
.95 Jy

    The pitch, roll, and focus correction (PRF) is limited to a range of azimuth and zenith angles because of the large correction we currently have and the limited throw of the tiedowns. During this run the sources were tracked rise to set and the PRF correction was turned on when the source was within the allowable range. This lets us compare the gain/SEFD with the PRF correction on and off.

The figures show the results of the measurements.

  • Fig 1 plots the gain in K/Jy versus azimuth and zenith angle.
    • The horizontal line separates the measurements that had the PRF on (above) and off (below). The vertical dotted line is transit. The unadjusted panels are in the SW (rising). The plot versus za has solid lines for rising (SW) and dotted lines for setting (SE).
  • Fig 2 plots the SEFD (Jy per Tsys) versus azimuth and zenith angle. Larger numbers are worse.


    • The source J1143+221 went from 3 K/Jy to 6 K/Jy within 1.5 degrees za when the PRF correction was turned on. This occurred in the SW portion of the dish were the panels have not yet been adjusted.
    The source J0827+293 went from 4 K/Jy to 7 K/Jy within 1 degree za when the PRF correction was switched on. This occurred in the SE where the panels have already been adjusted. Independent of the correctness of the flux or the calValues, the gain is increasing 75-100% when the PRF correction is being applied.

    You can see the contribution that the panel adjustments have made to the gain by looking at  J0827+293 (red) around  12 degrees za. The lower * are made rising (SW) while the upper * are from the (SE). The gain difference is about 10% (of course these two positions actually see a mixture of adjusted/unadjusted panels since the beam covers a large area).

    The SEFD is getting down below 5 Jy/Tsys.

    The sources are giving consistent results so the fluxes are probably pretty good. J1143+221 does not do quite as well as the other sources. This is because it transits at a very low za and sees a large fraction of panels from the North section of the dish that have not yet been adjusted. 

    processing: x101/010627/doit.pro
    plotting  : x101/010627/doplot.pro
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