1. A method for controlling the temperature of the calibration volume of an apparatus for comparative calibration of temperature sensors to a target temperature, the method comprising the steps of: providing a calibration apparatus having heat sources and/or heat sinks which are in thermal contact with a calibration volume through one or more heat conducting parts, the calibration apparatus further having at least one temperature sensor disposed in the calibration apparatus; estimating a true thermal state using a Kalman filter, wherein the Kalman filter is supplied measured values from the at least one temperature sensor disposed in the calibration apparatus; and calculating a future thermal state using a thermal model of dynamics of thermal states of the calibration apparatus, wherein the thermal model includes at least one control and manipulated variable, the at least one control and manipulated variable having at least two possible settings.