Why have multiple sensor arrays?
MALMS has one array of sensors to measure light (the Light Array) and another (the Position Array) to locate each light source and determine the offset of the measurement system when over the light. MALMS works to the ICAO specified measurement method and calculates Average Intensity from measurements taken in the Main Beam area – trigonometry then defines the position that the Light Array should be mounted relative to the light source. For services (such as TDZ) where the beam is displaced from the axis of the runway (TDZ are either toed towards or away from the runway centre line) the Light Array must also be displaced. Since the position array is designed to measure offset relative to the ideal position it should be positioned over the axis of the light source even if the beam is toed. Therefore, the two sensor arrays have to move relative to each other as the system is configured for different beam characteristics.
