Alfa spider scans taken at 1665 Mhz

links to plots:
total power versus sample along the strips.
the system performance.

    100 Mhz filters centered at 1665 Mhz were installed after the dewar on  alfa. Heiles calibration scans (spider scans) were then taken centering each alfa beam on the source 3C43 (the flux used was 2.46 Jy at 1665 Mhz). 24 spider scan patterns were taken but only 13 of these were analyzed (the other 11 patterns spanned multiple files and were not analyzed). An attempt had been made to measure the alfa cal values at 1665 Mhz but the cal coupling into the horn at 1665 is very poor. The program ended up using the cal values at 1520 Mhz so the gain and Tsys were not accurately measured.
    Each pattern contains 4 strips of 6 beam widths each (about 3.5 Amin per beam width). While tracking the source, the four strips drove :

 The drive time was 60 second per strip with 1 second sampling using the wapps.
    The first set of plots  shows the total power versus sample along the strips. Each page is a separate pixel of the array. Black is polA and red is polB. Dashed green lines separate the four strips. Each division on the x axis is 3.5 arcminutes (about 1 beam width).
      The sidelobes for some of the pixels are large (-6 db). This may in part be do to the pointing error that did not take us through the source peak. If you believe the pointing errors from the fits, then a 56 asec error gives a 1 db loss. You can also clearly see the coma lobes in most pixels.

    The second set of plots show the system performance. They were generated after passing the measured data thru the heiles calibration software. This fits individual gaussians for each strip (the main beam and two sidelobes). It then does a 2d fit for the beam. The values for each pixel are plotted in a separate color.


processing: usr/a1800/ohcalib/,