The calibration of a small, low-cost thermal infrared radiometer

Two Everest 4000A radiometers were used to measure sea surface temperatures in the Southern Ocean from the RSV Aurora Australis during the periods 7 August 1993– 9 October 1993 and 1 January 1994–1 March 1994. On four separate occasions, the radiometers were calibrated under controlled laboratory conditions using a ThermosTM 60-L cooler; a cool room and a ConthermTM unit. The calibration results were best when the radiometers and calibration target were allowed to come to equilibrium at a set temperature, with root-mean-square differences of 0.1°C between the measured and actual target temperatures. When the radiometers were operated under conditions of rapid temperature change, the root-mean-square differences were found to be as large as 0.6°C. The bias error of the radiometers was found to have changed subsequent to each of their deployments in the Southern Ocean, and this underlines the importance of monitoring changes in the offset of the radiometers in the field.