Simulation of infrared detection range at fog conditions for Enhanced Vision Systems in civil aviation

The DLR project ADVISE (ADvanced VIsual System for Situation Awareness Enhancement) deals with development, simulations and testing for an Enhanced Vision System (EVS) for visual pilot assistance. Within the frame of the project ADVISE, model calculations in the infrared spectral region have been performed to investigate the influence of low visibility conditions, especially fog, for air traffic during landing approaches. The objectives of this paper are to find out whether the use of IR cameras for an EVS can improve the visibility at defined conditions of ICAO standard visual range categories CAT I, II, IIIa and IIIc for landing approaches. The calculations are carried out with the atmospheric radiative transfer model MODTRAN Version 4.0. The IR detection range is calculated in the atmospheric windows 3–5 μm and 8–12 μm and compared to the visual range defined at 0.55 μm. The sensor properties are simulated with the model TTIM (TACOM Thermal Image Model) for a specific IR camera type Thermovision 570 operating in the spectral band 8–12 μm. The influence of various climatic and seasonal meteorological conditions, aerosol types and target parameters, such as temperature and size, on the IR detection range is taken into account.