Study of sunshine, skyshine, and earthshine for aircraft infrared detection

Investigations are reported on infrared (IR) signature studies from internal sources of aircraft and helicopters, e. g. engine heated surfaces and exhaust plume. Due to the increasing sensitivities of IR sensors, irradiances from external sources are investigated here, namely sunshine, skyshine, and earthshine. Their role in determining the IR contrast in the 1.9-2.9, 3-5, and 8-12 mu m bands is studied. Estimation of earthshine is emphasized because of its tactical significance in low altitude missions and IR imaging studies. A comparison of IR radiance from aircraft's rear fuselage due to internal and external sources shows different roles in the 3-5 and 8-12 mu m bands. The important roles of earthshine and temperature-based radiance of aircraft surfaces are identified in the 8-12 mu m band.