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Дата изменения: Wed Aug 15 16:30:52 2001
Дата индексирования: Tue Oct 2 06:10:16 2012
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Cband performance after northern half of the dish adjusted.

july,2001

     The adjustments to the panels in the northern half of the dish were completed early in aug01. On 02aug01 and 09aug01 southern sources were tracked at cband to test the performance of the telescope. The standard "heiles" pattern at 4500,4860,5000, and 5400 Mhz was used to measure the beam parameters. The sources tracked were:
 
source
flux at 4860
B1416+067
  
B1638+124
1.089 Jy
B1857+129
.97 Jy
B2041+170
.24 Jy
B2314+038
1.37 Jy
B1641+173
1.72

The data was taken between 18 hours and 4 hours AST.  The average height of the platform was being tracked with the tiedowns while this data was taken.

The figures show the results of the measurements.

  • Figure 1 plots the total power za pointing error versus za (top) and azimuth (bottom) for 4500 Mhz. The solid lines are rising and the dotted lines are setting.
  • Figure 2 shows the azimuth pointing error versus za (top) and azimuth (bottom) for 4500 Mhz. There is a large az error for the 17 degree dec sources when they transit. The gains for za less then 2.5 should probably be ignored.
  • Figure 3 plots the gain in Kelvins/Jansky versus za for the 4 frequencies. Solid colors are rising and dotted colors are setting. The black dotted lines are just a reference grid. The setting gains are higher than the rising gains. This is expected since the south west quadrant of the dish  has not had its panels adjusted yet. The rising sources will see this more than the setting ones.
  • Figure 4 is the gain versus azimuth. There is a noticeable step in the gains of the 12 degree dec sources at an azimuth of - 60 degrees. This jump was also seen at sbn in the  SEFD for J1859+129 (B1857+129). It was not there before the tertiary motors were installed (and the tertiary was reset).
  • Figure 5 has the gain for 4500 Mhz (top) and the gain after correction for any pitch, roll, and focus error (done in software using a model). The current model is not doing a large correction at these az,za's. B1641+170 is leveled, but there is still an opening angle between rise and set for the sources. We need to use the aug01 theodolite data to make a new pitch, roll, focus model.
  • Figure 6 has the System Equivalent Flux Density (SEFD) in Jy/Tsys plotted versus za. The excursion of the green line is from the pitch, roll, focus error.
  • Figure 7 plots the SEFD versus azimuth.
    • The gains look very good.  They are close to 8 K/Jy. Of course the gain measurement requires that our cal values are correct. The SEFD which only relies on the flux is  4 Jy/Tsys at 4500 Mhz. This is consistent with 8 K/Jy and a Tsys of 32 K (which is the value the cals give).

    You can compare this data  to the cband data taken in jan01 after the 1st set of tieback adjustments were done and with 3C48 on 28jun01 when the SE quadrant adjustment was finished. The SEFD for 3C48 at 15 degrees za was 8 Jy/Tsys on 28feb01, 7 Jy/Tsys on 28Jun01 and is 4.5 to 6 Jy/Tsys now.

    For the current set of sources, the flux for B1638+124 looks a bit high. 

    processing: x101/010802/doit.pro
    plotting  : x101/010802/doplot.pro
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