1. A method for controlling a temperature of a 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 at each time increment over a period of time using a Kalman filter and a thermal model of dynamics of thermal states of the calibration apparatus, the true thermal state including at least one temperature of the at least one temperature sensor, wherein the Kalman filter is supplied measured values from the at least one temperature sensor disposed in the calibration apparatus and 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; calculating a mean square deviation of the at least one temperature of the at least one temperature sensor from the target temperature using the estimated true thermal state and the thermal model of the dynamics of the thermal states of the calibration apparatus for the at least two possible settings of the at least one control and manipulated variable at each time increment over the period of time; setting, at each time increment over the period of time, the at least two possible settings of the at least one control and manipulated variable for the calibration apparatus, such that the calculated mean square deviation is at a minimum; and whereby with the at least two possible settings of the at least one control and manipulated variable being set at each time increment over the period of time, the at least one temperature of the at least one temperature sensor reaches the target temperature and holds the at least one temperature of the at least one temperature sensor at the target temperature.