Aircraft Signature Studies Using Infrared Cross Section and Infrared Solid Angle

Aircraft infrared (IR) signature studies are complex, due to their dependence on several parameters, e.g., line of sight (LOS) and viewing aspect (LOS^). There is no equivalent counterpart of the well-known radar cross section (RCS) that can be easily used for obtaining IR lock-on range, RLO,λ1−λ2. This study introduces the concept of IR cross section (IRCS)λ1−λ2 of complete aircraft as seen by seeker in λ1–λ2 band in LOS^ and of aircraft part in an orthogonal view. The IR solid angle (ωIR,λ1−λ2) subtended by (IRCS)λ1−λ2 of complete aircraft and of an aircraft part is also introduced, which is the basis for redefined general criterion for lock-on by IR-guided missile. Equality based on ωIR,λ1−λ2 at aircraft part level and at complete aircraft level is the basis for obtaining RLO,λ1−λ2 of complete aircraft in terms of its (IRCS)λ1−λ2. Dimensionless scalar factor, ΠIRCS,λ1−λ2, converting visual area to (IRCS)λ1−λ2 is studied, for temperatures ranging from close to ambient to maximum afterburning (reheat) mode of aeroengine. The ΠIRCS,λ1−λ2 enables assessment of effectiveness of IR seekers with single or dual bands, for all-aspect engagement and for rear-view only.