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I'll continue to monitor this non-thermal pedestal drift.
The following plot shows the non-thermal pedestal drift for 50 days since Jun 28. It also shows the pedestal and real temeperatures for cold therma balance of Observatory TVAC (this measurement was done on January 20, but on the plot it was shown at launch date Jun 11).
The plot shows that the difference between pedestal temperature and real temperature has deviations from pure exponential behaviour, when temperature was significantly different from nominal (LAT power OFF). The prelaunch point looks very different from orbit behaviour - the reason is not clear.
I plan to add more pre-launch measurements on this plot.
Two next plots show the non-thermal pedestal trend over 103 days in normal and zoomed vertical scale.
The slow decrease of pedestal temperature while real temperature is constant continues at the rate ~0.5 degree/ month - this corresponds to the pedestal drift of 1.5 ADC units per month in the most sensitive channels.