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In this paper the results of development and investigation on textile-based radar absorbing materials for protection against battlefield radar are presented. This research has been carried out within the Project “Adaptive Camouflage for the Soldier” (ACAMSII) which has received funding from the European Union’s Preparatory Action for Defence Research—PADR programme under grant agreement No 800871. To develop the fabrics with microwave shielding and absorbing properties samples of woven fabrics were coated with compositions containing inherently conducting polymers (ICPs), carbon-based formulations or their mixtures. For coating screen printing and knife-over-roll techniques were applied, as our aim was to develop the fabrics coated with conductive layer only on the back side of camouflage pattern printed fabric, that it could be integrated in the military camouflage clothing system. In the radar threat evaluation, as a part of ACAMSII project, it was pointed up that a major threat to dismounted soldiers are battlefield radars commonly operating within X and Ku-bands. Consequently, the investigation of reflection and transmission properties of developed textile fabrics was performed in a frequency range of 6–18 GHz, which cover the defined frequencies relevant to the application. It was found that shielding effectiveness (SE) as well as absorption properties depend not only on the amount and type of conductive paste topped on the fabric, but also resides in the construction parameters of fabrics and their finishing before coating.

The development of new sensing abilities, such as hyperspectral sensors, small man-portable infrared sensors, battlefield radars and faster AI based data processing requires new capabilities of camouflage materials. Military systems also have to work in changing environments calling for adaptivity. ACAMSII is an EU funded project within the Preparatory Action for Defence Research (PADR) programme under grant agreement No 800871. Scientists from Sweden, Germany, Portugal, France, Lithuania and the Netherlands cooperate in the project. ACAMSII conducts applied research on improved Camouflage for the Soldier with purpose to provide increased survivability in diversified environments. The ACAMSII multifunctional camouflage demonstrator consists of three main parts: • The IR adaptivity is realized by integrating phase changing and low emissivity materials in the printed camouflage patterned textile. • Adaption to background colours and lighting conditions in the visible range is managed by operating and driving light emitting diodes (LEDs) embedded in a panel of clothing textile material. The LEDs are controlled by means of a camera and a light sensor placed in the back. Thermochromic materials give further adaptation. • Woven fabric is coated with microwave shielding and absorbing materials reduces the radar signature. For a soldier combat system, not only camouflage properties are of importance but also the comfort properties of the system is evaluated. In this paper emphasis is put on military needs (top-down or market pull) and scientific aspects and technical readiness level of available technology and materials (technology push or down-up), on how to build a consortium in an international collaboration during a pandemic. The concept of EDA Overarching Strategic Research Agenda is introduced and the projects relation to this explained. Only general aspects and results from the three-year project, ending 2021, is presented here whereas specific details of the camouflage system are presented in other papers presented during the session.

As the sensor technology for polarimetric imaging is advancing into more robust commercial systems such sensors could soon be expected for, e.g., military surveillance and reconnaissance applications in addition to more conventional sensor systems. Thus, there might be an upcoming need to understand limitations on present camouflage systems to meet this new sensor threat. Some of the reasons why polarimetric imaging has drawn attention is the ability to achieve a higher contrast for artificial surfaces against natural backgrounds, by analyzing the degree of linear polarization, which in this work has been analyzed for different types of surfaces as a function of wavelength. We also compare with the polarimetric vision of horse-flies and other aquatic insects via the polarization properties of different colors of horse coat hair in order to give some further insight into polarimetric vision techniques developed by nature. In this work we have used different measurement techniques, such as angle dependent polarimetric spectral directional hemispherical reflectance and polarimetric imaging.

Polarimetric imaging sensors in the electro-optical region, already military and commercially available in both the visual and infrared, show enhanced capabilities for advanced target detection and ...

In this work a spectral designed coating from SPECTROGON is evaluated. Spectral design in this case means that the coating has a reflectivity equal to one at 3-5 and 8-12 microns were sensors operate and a much lower reflectivity in the other wave length regions. Three boxes are evaluated: one metallic, one black-body and one with a spectral designed surface, all with a 15 W radiator inside the box. It is shown that the box with the spectral designed surface can combine the two good characteristics of the other boxes: low signature from the metallic box and reasonable inside temperature from the black-body box. The measurements were verified with calculations using RadThermIR.

This new security development is expected to increase interest fromNorthern European states in supporting the development of conceptually newstealthy ground platforms, incorporating a decade of advances in technology andexperiences from stealth platforms at sea and in the air. The scope of thiscase study is to draw experience from where we left off. At the end of the1990s there was growing interest in stealth for combat vehicles in Sweden. Anambitious technology demonstrator project was launched. One of the outcomes wasa proposed Systems Engineering process tailored for signature managementpresented to SPIE in 2002.(Olsson et.al, A systems approach…, Proc. SPIE 4718 )The process was used for the Swedish/BAE Systems Hägglunds AB development of amultirole armored platform (The Swedish acronym is SEP). Before development wascompleted there was a change of procurement policy in Sweden from domesticdevelopment towards Governmental Off-The-Shelf, preceded by a Swedish ArmedForces change of focus from national defense only, towards expeditionarymissions. Lessons learned, of value for future development, are presented. Theyare deduced from interviews of key-personnel, on the procurer and industrysides respectively, and from document reviews.

Optical properties of natural photonic structures can inspire material developments in diversified areas, such as the spectral design of surfaces for camouflage. Here, reflectance, scattering, and polarization properties of the cuticle of the scarab beetle Cyphochilus insulanus are studied with spectral directional hemispherical reflectance, bidirectional reflection distribution function (BRDF) measurements, and Mueller-matrix spectroscopic ellipsometry (MMSE). At normal incidence, a reflectance (0.6–0.75) is found in the spectral range of 400–1600 nm and a weaker reflectance 1600 nm . A whiteness of 𝑊=42 is observed for mainly the elytra of the beetle. Chitin is a major constituent of the insect cuticle which is verified by the close similarity of the measured IR spectrum to that of 𝛼 -chitin. The BRDF signal shows close-to-Lambertian properties of the beetle for visible light at small angles of incidence. From the MMSE measurement it is found that the beetles appear as dielectric reflectors reflecting linearly polarized light at oblique incidence with low gloss and a low degree of polarization. The measured beetle properties are properties that can be beneficial in a camouflage material.

In development of visual (VIS) and infrared (IR) camouflage for signature management, the aim is the design of surface properties of an object to spectrally match or adapt to a background and thereby minimizing the contrast perceived by a threatening sensor. The so called 'ladder model" relates the requirements for task measure of effectiveness with surface structure properties through the steps signature effectiveness and object signature. It is intended to link materials properties via platform signature to military utility and vice versa. Spectral design of a surface intends to give it a desired wavelength dependent optical response to fit a specific application of interest. Six evaluation criteria were stated, with the aim to aid the process to put requirement on camouflage and for evaluation. The six criteria correspond to properties such as reflectance, gloss, emissivity, and degree of polarization as well as dynamic properties, and broadband or multispectral properties. These criteria have previously been exemplified on different kinds of materials and investigated separately. Anderson and Åkerlind further point out that the six criteria rarely were considered or described all together in one and same publication previously. The specific level of requirement of the different properties must be specified individually for each specific situation and environment to minimize the contrast between target and a background. The criteria or properties are not totally independent of one another. How they are correlated is part of the theme of this paper. However, prioritization has been made due to the limit of space. Therefore all of the interconnections between the six criteria will not be considered in the work of this report. The ladder step previous to digging into the different material composition possibilities and choice of suitable materials and structures (not covered here), includes the object signature and decision of what the spectral response should be, when intended for a specific environment. The chosen spectral response should give a low detection probability (DP). How detection probability connects to image analysis tools and implementation of the six criteria is part of this work.