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I found MIP peak and Pedestal values once every four weeks from week 28 to week 108 (21 data points). I plotted this data against against time units of 10,000 hours. I then fit a straight line to the data. The slope of this line is the rate of change of the calibration per 1.14 years, so by dividing by 1.14 we find the change per year
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MIP peaks
The pedestals exhibit great stability. This plot MIP peak values exhibit no systematic drift. The plots below show a histogram of the slope of the trend line (in units of MIP's per year).