Galfa pixel 4a/6a switched may05

    The cables for pixel4a and pixel6a (count from 0)  from the distribution amplifiers in the receiver room to the galfa spectrometer were switched sometime in early may05 (or late apr05). This meant that when  looking at the data offline:

• 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). The last "good" data set that showed know cable switch was 12dec05. The next data set available after this was 02may05. The second data set showed the cables being switched (i didn't find any data between these two dates to test).
    The plots show the total power drifts versus time after and before the switch (.ps) (.pdf). Each pixel is plotted in a different color. For each color there are two strips: polA and then polB over plotted:

• Fig 1 Top: 02may05. The purple strips are pixel4(a,b) while the light blue is pixel6(a,b). The dotted lines around 400 show that the same source is moving through pixel 4 and pixel 6. The dotted line at 465 shows another source that is transiting pixel 4 and pixel 6 simultaneously.
• Fig 1 Bottom: These are calibration scan data taken on 12dec05. The double traces of each color track each other.

Summary:

• The galfa cables for pixels 4a,6a were switched sometime after 12dec04 and before 02may05 (probably in late apr05).
• The problem was corrected on 31may05 at 11am ast.
• The wapp alfa data was not affected by this problem.

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