Variation of the temperature of the back-end with time, as measured by sensor LM207332 (placed near the back-end amplifiers of LFI27M and 27S). The two major thermal events that happened during the period of the nominal mission are clearly visible here: (1) 258 days after launch the transponder antenna switched from a on/off duty cycle of 24 h to being always kept on, and (2) 456 days after launch we switched to the other sorption cooler used to cool the focal plane.