Intrinsic Infrared Radiation of the Sea Surface

Abstract

Prologue-The infrared contrast of ships at sea is of importance for those who want to detect, identify and achieve target acquisition and for those who want to protect to enhance target vessel's first strike capability and hence its survivability. Infrared signature control or stealth technology is changing the face of naval warfare and is rapidly becoming a key performance parameter in warship design. The infrared contrast is determined by a large number of parameters. Temperatures of the ship structure and the ambient sea and air are important. But the infrared and visible signature is due not only to target emissions but to the immediate target background. Infrared signature designs are driven by signature generation mechanisms and threat sensors characteristics. Definition of threat sensor types (operating bands, resolution capability) helps to focus infrared and visual signature control on the spectral regions and spatial dimensions of greatest interest. One of the more common divisions of the visual or infrared signature definition is the separation based on so-called imaging versus non-imaging sensors. Imaging sensors threats are represented by the human eye and aids such as televisions, FLIRs (forward-looking infrared) and image intensifiers. These threats possess the ability to resolve and process silhouette and internal target pattern detail. Non imaging sensors depend on target signal strength and background separation. Nonimaging sensor threat are represented by missile seekers, IRSTs (infrared search and track) and terminally guided submunitions. The more recent generation IR missile seeker threats use the 3 to 5 µm band, future threat seekers are likely to use imaging focal plane arrays. Infrared search and track systems work in the same 3 to 5 µm band as do missile seekers. Future

Theoretical Study on Microwave Scattering Mechanisms of Sea Surfaces Covered With and Without Oil Film for Incidence Angle Smaller Than 30°

“…2 shows the simulated root mean square (rms) slopes of clean and polluted sea surfaces versus wind speed at 10-m height (U 10 ). The corresponding rms slopes can be derived by [36] Upwind:…”

“…The autocorrelation function W (r) can be expressed in polar coordinates with the sea spectrum [36] W (r) = W (r, ϕ) = W 0 (r ) − cos(2ϕ)W 2 (r ) where S 0 (k w ) denotes the omnidirectional part of sea spectrum, k w is the wavenumber of the sea wave. k d is set as k i /3 in this article.…”

Scattering from canonical objects above a sea-like one-dimensional rough surface from a rigorous fast method

“…With a sampling step Dx 2 ¼ 0 /10, we set k max ¼ 20/. In [32], a criterion is given to insure that the generated surface spectrum can be assimilated to the theoretical one (the inferior boundary reaches the value of 10 À5 of the maximum): k min 0.28k pic in which k pic ¼ 2 g=u 2 10 is the wavenumber of the most energetic wave. ¼ 0.84 for a fully developed sea and g ¼ 9.81 m s À2 .…”

Doppler Spectrum Mathematical Model of Signal Scattering From Sea Surface at Low Grazing Angles

“…Модель морской поверхности. Для описания морской поверхности существуют различные модели -линейные и нелинейные, учитывающие пространственный спектр морского волнения [10]- [13].…”

“…В качестве пространственного спектра морского волнения выбираем спектр Эльфохейли, позволяющий более точно по сравнению с другими моделями спектров учитывать вклад гравитационно-капиллярных и капиллярных волн в морское волнение [12], [13].…”