Green Function Inversion for Deep Atmospheric Turbulence Compensation

For applications like tactical laser weapons which involve imaging or transmitting energy via lasers over long paths near the ground, the cumulative atmospheric turbulence effects exceed what conventional adaptive optics technologies can handle. To compensate for moderate to severe deep turbulence effects OPC has developed a new technique called Green’s Function Inversion (GFI). GFI can be used to characterize the transmission path between a high energy laser (HEL) and a target. Once the path is well characterized, the HEL beam can be adjusted to form a very high quality beam at any position. Even very high Greenwood frequencies can be accommodated using a ripple update. It is especially useful with conformal fiber laser arrays as a HEL source. During Phase I, we will perform a detailed wave-optic simulation of the GFI technique to demonstrate its performance under AF engagement conditions, with the sample scenario as a starting point. The ability to generate a target image suitable for aimpoint selection and maintenance will be shown and the ability to place a high quality hit spot on the designated aimpoint evaluated including point ahead offsets. Finally, a prototype flight design will be generated and a lab experiment laid out for Phase II. BENEFITS: GFI beam control is well suited to phasing and correcting a conformal array of HEL fiber lasers through turbulence. Besides the air-to-air engagements, the technique also applies well to air-to-ground and ground-to-air scenarios, as well as applications such as imaging and aim point maintenance through long horizontal paths. The speckle processing used in GFI is well suited to HEL diagnostics in that an image of the hit spot can be produced in real-time. NGST is our strategic partner in this effort which provides an excellent pathway for technology insertion.