The present invention describes a method for determining a value for the temperature, radiation, emissivity, transmissivity and/or reflectivity of an object (2) such as a semiconductor wafer in a rapid heating system (1), wherein an output signal from a radiation detector (50) which records temperature radiation from the object is used as a measurement value, and wherein prediction values for the measurement values are calculated in a model system (100). The development over time of the measurement values is compared with the development over time of the prediction values and the measurement value is corrected if the difference exceeds predetermined threshold value.