Method of calibrating a heater system

A system for calibrating a heater system for heating a surface of a structure, the system comprising:

• the structure;
• the heater system, including:
• a heater element;
• a temperature sensor proximate the heater element for outputting a signal indicative of the temperature of the heater element;
• and
• a controller for controlling the supply of power to the heater element in dependence on the signal to maintain the temperature of the heater element at a first substantially constant temperature;
• a reservoir for immersing the structure in a fluid for maintaining the surface of the structure at a second substantially constant temperature;
• a power supply for supplying an amount of power to the heater element;
• and
• a sensor for receiving the signal from the temperature sensor and determining a temperature at the temperature sensor, whereby to allow the determination of a setpoint temperature for controlling the heater element in dependence on the signal and the second substantially constant temperature.