Small craft identification discrimination criteria (N₅₀ and v₅₀) for visible and infrared sensors in maritime security

The new emphasis on Anti-Terrorism and Force Protection (AT/FP), for both shore and sea platform protection, has resulted in a need for infrared imager design and evaluation tools which demonstrate field performance against U.S. Navy AT/FP requirements. In the design of infrared imaging systems for target acquisition, a discrimination criterion is required for successful sensor realization. It characterizes the difficulty of the task being performed by the observer and varies for different target sets. This criterion is used in both assessment of existing infrared sensor and in the design of new conceptual sensors. In this experiment, we collected 12 small craft signatures (military and civilian) in the visible band during the day and the LWIR and MWIR spectra in both the day and the night environments. These signatures were processed to determine the targets' characteristic dimension and contrast. They were also processed to bandlimit the signature's spatial information content (simulating longer range) and a perception experiment was performed to determine the task difficulty (N50 and V50). The results are presented in this paper and can be used for Navy and Coast Guard imaging infrared sensor design and evaluation.