Applications with a non-cooperative Target
While applications with cooperative targets are of significant interest to Nutronics, Inc. and our systems developed for applications with cooperative targets form the basis of all of NAO Systems technology solutions, the area that has been our primary research and development focus has been to develop and demonstrate a solution to the problem of compensation in the presence of branch points in the phase function when the Rytov Number exceeds 0.2 with non-cooperative targets. We largely consider the problem of compensation with cooperative targets in this regime “solved” for roughly 10 years with the recognition of the superiority of interferometric based wavefront sensors such as the Point Diffraction Interferometer (PDI) or Self-Referencing Interferometer (SRI). The fact that these sensors have performance that is invariant with scintillation defined a clear development path, and the subsequent research and development leading to our core product line followed a natural and logical path . In contrast, development of a solution path for the strong scintillation regime with non-cooperative targets has been far from straightforward and has defined the NAO Systems Imperative.
Nutronics, Inc. provides Hartmann sensor based AO systems for the weak scintillation regime (when the Rytov Number is less than 0.2) and has developed a breadboard laboratory demonstration of the Adaptive Tactical Laser System (ATLAS) for operation in the strong scintillation regime (when Rytov Number is greater than 0.2). These systems usually involve reasonably high power levels and will invariably need to be customized to the application of interest and Nutronics can discuss customer requirements on a case by case basis.
ATLAS is an innovative variation of a compensated beacon adaptive optics (CBAO) system. As discussed in the NAO System Imperative, CBAO systems are not ensured to converge to a focused spot on the target, as illustrated in Figure 1.
Figure 1: AO compensation, even when the beacon laser is pre-compensated by the AO system to provide better focusing of the beam on the target is not effective when the Rytov Number exceeds 0.2 and in particular is very poor in the Deep Turbulence regime when the Rytov Number exceeds 1.0.
In contrast, as illustrated in Figure 2, Nutronics, Inc.’s ATLAS beam control system achieves performance comparable to that of a point source beacon, even in Deep Turbulence conditions. Performance of a Hartmann sensor based system is significantly worse than that for ATLAS. ATLAS does not utilize Target-In-the-Loop (TIL) methods such as multi-dither or stochastic parallel gradient descent and as such does not suffer from time of flight data latency. This allows ATLAS to be compatible with high temporal and spatial bandwidth operation – both critical for the next generation of applications of AO in demanding turbulence conditions.
Figure 2: Wave optical simulation based investigation of ATLAS with Rytov Number = 1.15 and D/rο = 13.1. ATLAS performance is predicted to be significantly better than performance with a Hartmann sensor and has performance nearly equivalent to that of a point source beacon based system.
As illustrated in Figure 3, Nutronics, Inc. has demonstrated ATLAS beam control in the laboratory with simulated atmospheric turbulence.
Figure 3: ATLAS Laboratory Demonstration in severe turbulence conditions with Rytov Number = 1.00 and D/rο = 7.52. The upper images of the laser on the target include both the Track Illuminator (TILL) and the Simulated High Energy Laser (SHEL) on the reflexite-augmented target while the lower images include only the SHEL to clearly indicate the effectiveness of compensation.
While ATLAS technology is just getting off the ground, please give us a call at 303−530−2002 or Email at firstname.lastname@example.org and we will be happy to discuss your application and needs. Many applications are well served by a more straightforward and lower cost Hartmann sensor based AO system and such systems can be offered as minor variations on our standard products.