Multiconjugate Adaptive Optics for Distributed Turbulence

Conventional aperture plane phase-only adaptive optics (AO) is becoming amature technology. We have had decades of experience with up-lookingapplications, where most of the turbulence is close to the aperture, and inrecent years there has been substantial progress in AO for near-horizontalpaths, with distributed turbulence, largely motivated by the Airborne Laser(ABL) Program. Progress continues, but the practical limits of conventionalAO technology for deep turbulence applications are beginning to becomeapparent. These relate to scintillation, high order anisoplanatism, phasebranch points, and the use uncooperative beacons for tracking and higherorder correction under conditions where these effects are prevalent.Conventional AO does not address scintillation or high order anisoplanatismat all, and branch points present serious practical difficulties even whenperfect sensing is assumed. Multiconjugate (MCAO adaptive optics is a lessdeveloped technology involving significant technical challenges, but thereare reasons to believe it may be able to ameliorate these problems, yieldingimproved performance over a wide range of conditions, and, more importantly,yielding acceptable performance in regimes where conventional AO fails. Forthe ABL this would translate into a longer maximum range, and killingmissiles that otherwise would have gotten past.It is anticipated that a multiple deformable mirror adaptive optics system successfully demonstrated under this research, with economical considerations folded in, would have both commercial and militaryapplications. The military applications include the ABL and follow-on systems, Relay Mirror, remote sensing, and any DoD programs utilizing adaptive optics in high scintillation. Other applications include airborne imaging (military and commercial),especially for reconnaissance and surveillance systems that must image through turbulent boundary layers. The commercial market includes such areas as astronomy (retrofitting astronomical sites), laser communication and power beaming. It is expected thatthe contractor will focus on Phase I designs that would maximize both the commercial potential and the military potential.