Advanced missile seeker technologies and missile propulsion systems with reduced electrooptical signatures constitute a serious threat to military platforms. Seekers using multiple spectral bands may be hard to jam using current countermeasure systems. Imaging seekers may have adaptive tracking algorithms to suppress the effect of current countermeasure strategies. Furthermore, countermeasures can only be used if a threat has been declared. Low-signature propellants in combination with the missile seen in head-on angle, where a bigger portion of the missile plume is shielded by the missile body, will make it extremely hard to detect the missile with current warning sensor systems. We report on the objectives and the status of the EDA CAT B project DEBELA (Detect Before Launch), which tries to address this threat, and which looked into potential technologies for future self-protection systems. The project focusses on within visual range threats and electrooptical sensors only. Candidate-technologies have been identified and tested in a field experiment on the premises of the Bundeswehr Technical Center (WTD 52) in Oberjettenberg, Germany.
In the spectral band typically lower than 290 nm, solar radiation doesn't reach the Earth surface due to ozone absorption. UV radiation of artificial sources can then be recorded with a high contrast, by day or night. Because of this property, this spectral domain is called "Solar Blind". Furthermore, many UV detectors work at ambient temperature and have high sensitivity. One can envisage to use UV sources as beacons, particularly to find one's way around in case of haze. Light scattering by atmospheric particulates and molecules gives rise to an aureole surrounding the source image which tends to reduce the contrast of the source with respect to the background. However, scattering phase functions of the haze droplets present a very important forward peak and spreading of detected signal is not as important as in case of a clear atmosphere where Rayleigh scattering predominates. Moreover, the range of UV radiation propagation is limited by the high ozone absorption cross section. All these physical phenomena have to be taken into account in order to evaluate UV radiation potential interest for landing aid under low visibility conditions. We present here different results on characterization of UV runway light, propagation of UV radiation in the atmosphere and on the use of different kinds of sensors that are necessary to assess this point.
In the atmosphere, light scattering by molecules, particulates and aerosols causes an aureole around point- like sources. In various meteorological conditions, the radiance field coming from this aureole can be a non- negligible part of the total detected signal by large Field Of View sensors. In the framework of aureole's study, we have developed a method based on Monte Carlo calculation. The corresponding code permits to deal with monochromatic point sources in the 240 to 300 nm spectral range. The source's intensity angular dependency is axisymmetric and the atmosphere is described as a plane-parallel medium composed of a user defined constituents profiles. Systematic tests have been performed in order to evaluate the influence of the different input data on aureole results, such as ozone and SO2 concentration values or ozone and aerosols concentration profiles. These computations will help us to define the set of meteorological parameters which need to e known accurately in order to compare computations with detected signals recorded during field experiments.
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