Cooling film’s suppressive effects on infrared system’s radiation noise in aero-thermal environment

Abstract

Infrared imaging systems are crucial for guidance in supersonic vehicles due to all-weather capability, high resolution and high sensitivity. However, the imaging quality can be significantly impaired by aerodynamic thermal radiation noise. This paper incorporates cooling film that effectively eliminates the interference originating from supersonic thermal environments. A radiative transfer calculation framework that utilizes a high resolution line-by-line method for precise computation of radiative transfer from the target to the sensors of the imaging system is proposed. Heat flux across individual pixels indicates that the optical window serves as the primary source of interference within the 3 to 5 µm range. Additionally, the implementation of a cooling film significantly diminishes radiation noise, reducing interferences originating from both the optical window and the shock layer by an order of magnitude. Spectral analysis of the pixel’s heat flux underscores the pivotal roles of CO2 and H2O in the absorption and emission processes within radiative transfer, thereby complicating the observations of remote sensing. Contrasting with the traditional spectral band model, our methodology affords wavelength-specific visualization of radiative intensities for both target and interference signals. This enhanced spectral resolution provides a foundational reference for significant enhancements in both the clarity and accuracy of the imaging system.