Compact and efficient antenna architectures are key enabler solutions for on-board electromagnetic applications (telecommunications, radars, electronic warfare, etc.). Current solutions use cumbersome mechanical systems, or expensive but flat electronically steered phased arrays. The main goal of the project is to develop a disruptive, modular and ultra-low-profile antenna architecture for the next generation of high data rate satellite communication systems for moving platforms. The proposed system will be developed in Ka-band to benefit from the high data rates offered by future satellite constellations. High data rates require the large bandwidth available at Ka-band but also extremely flat and steerable antennas to be integrated on the fuselage of moving platforms (airplanes, drones, missiles, trains, etc.). The main technical and scientific challenge of the project is the development of an extremely flat antenna architecture able to steer in a fast and efficient way its main beam over a large angular sector (> ± 65°) and wide band (20% relative bandwidth centered at 20 GHz for the downlink). The KAPLA project will develop and integrate two very innovative building blocks at the core of the proposed novel architecture. The proposed architecture will be validated experimentally to demonstrate scanning performances beyond the state-of-the-art. In details, these building blocks are: - An extremely low profile beam-forming network (BFN) using leaky-wave modes, - A thin deflector based on artificial materials and made of novel hybrid metal-dielectric cells at sub-wavelength scales. These elements will be fabricated using: - Low-cost PCB technology for the leaky-wave BFN using guided structures (substrate integrated waveguide (SIW), or parallel plate waveguide), - Novel additive manufacturing processes for metallic/polymer elements for the deflector, as this element cannot be manufactured with standard fabrication processes. This hybrid and pragmatic approach and the proposed modular architecture will guarantee a dramatic price reduction with an enhanced modularity of the system fulfilling stringent requirements for civil and military needs. The civil and military stakes of the project are clear. Satcom communications are essential for civil (e.g. high data links for flight entertainment) and military applications (e.g. drone communication). The KAPLA project will address both needs with a single antenna concept operating in the military and civil bands (transmitting or receiving band) to reduce drastically the development and industrialization time and thus the final cost of the product. The economic stakes are also impressive. The civil and military market for Satcom applications is growing at a fast and constant pace. The KAPLA project will guarantee the excellence of the civil and defense French industry in such competitive field facing a strong American competition.