Per LLO aLOG 36022, I've added external temperature sensors to the CO2 lasers. The channel they are attached to are H1:TCS-ITMX(Y)_CO2_TEMP_SPARE. These names will eventually be changed to TEMP_LASER_EXTERNAL. They are clamped in place on the top of the laser chassis immediately behind the front end of the laser.

They are reading back temperatures of 19.65C and 20.02C for CO2X and CO2Y, respectively.