Galfa pixel 4a/6a switched jul05

    The cables for pixel4a and pixel6a (count from 0)  from the distribution amplifiers in the receiver room to the galfa spectrometer were switched on 11jul05  (after 8 am AST). They were returned to the normal order on 19jul05 (12:00 AST). The data going to the wapps were never switched. This meant that when  looking at the galfa data off line:

• pixel 4a spectra would be in the location of pixel6a
• pixel 6a spectra would be in the location of pixel4a.

    Continuum sources drift/move through the alfa beams at different times since the beams point at different locations in the sky.  600 second total power scans showed that pixel 6a and pixel 4b had continuum sources moving through the beams at the same time (6b and 4a also showed this).

    On 11jul05 a2011 took data using the wapps and using galfa. The plot shows the total power drifts versus time after the cable switch (.ps) (.pdf). Each pixel is plotted in a different color.
 

• Fig 1 wapp data. The top plot has the 7 pixels for polA. The bottom plot is polB. The light blue trace is pixel 6.  A continuum source moves through pixel 6 around 18.981 hours. The source appears at the same time in polA and polB.
• Fig 2 galfa data. The top plot has the 7 pixels for polA. The bottom plot is polB. The continuum source at 18.981 is now in pixel 4A and pixel 6B. It should have been in pixel 6A and 6B.

Summary:

• The galfa cables for pixels 4a, 6a were switched on 11jul05 between 8 am and 16pm (ast).
• The cables were put back in the proper order on 19jul05 at 12:00 pm (ast).
• The wapp alfa data was not affected by this problem.
• When processing galfa data for this date range, you should interchange the spectra for pixel 4a and pixel 6a. The value in the data headers should not be changed.

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