Results of a campaign to measure boundary layer/lower troposphere turbulence quantities over New Mexico's Tularosa basin are described in a companion paper. The present contribution outlines the technical developments that enabled these measurements. Basically, instrumented 'payloads' were carried aloft using either a relatively large aerodynamic blimp or a large parafoil kite. The choice between these platforms was dictated by wind velocity. The kite size was determined by the payload weight and the wind velocity. In addition to providing a brief history in CU involvement in kite/blimp atmospheric measurements, we will outline launching methods, tether winching techniques, and payload attachment schemes that were used during the WSMR campaign. Although very low wind conditions during the New Mexico test precluded the use of payloads up and down the kite tether under reasonable wind conditions. We also describe (1) the instrument package designed to measure in- situ temperature and velocity fluctuations, and (2) the 'basic payload' that measures standard atmospheric variables. System operation is illustrated via examples of the resulting data set.

The calibration procedure for a hot-wire anemometer system operating in a non-isothermal pressure-variant flow field is presented. Sensing of atmospheric velocity and temperature fluctuations from an altitude-variant platform using hot- wire anemometry equipment operating in both constant- temperature and constant-current modes requires calibration for velocity, temperature, and atmospheric pressure variations. Calibration tests to provide the range of velocity, temperature and pressure variations anticipated during Air Force Research Lab, Directed Energy Directorate- sponsored kite/tethered-balloon experiments were conducted and the result of these tests presented. The calibration tests were performed by placing the kite/tethered-balloon sensor package on a vehicle and driving from Kirtland AFB, NM to the top of Sandia Crest, a 10678 ft mountain range to the east of Albuquerque, NM. By varying the velocity of the van and conducting the test at different times of the day, variations in velocity, temperature and pressure within the range of those encountered during the kite/tethered-balloon experiments were obtained. The method of collapsing the calibration data is presented. Problems associated with collecting hot-wire anemometry data in a non-laboratory environment are discussed. Example data sets of temperature and velocity collected during the kite/tethered-balloon experiments are presented.

Results of the refractive index structure parameter (C_T²), C_n², and the eddy dissipation rate, (epsilon) , derived from the velocity structure parameter, C_v², are presented from high speed fluctuation measurements taken using a kite/tethered-blimp platform in the Tularosa Basin at White Sands Missile Range, NM during the spring of 1998. Comparisons of different sensor measuring the same parameter are displayed and discussed. Salient features of the sensors and the kite and blimp platforms are outlined. Long term measurements of high speed fluctuations of temperature and velocity are shown and intermittency of turbulence is discussed. The nature and statistics of turbulence inside, outside, and at the boundary of a turbulent layer are also shown and interpreted. Observations in the entrainment zone at the top of the planetary boundary layer are shown and similarities of characteristics found in the tropopause region with these boundary layer features is discussed. The diurnal variation of turbulence is presented with particular emphasis on the transition period from the end of daytime convection to development of the stable nocturnal boundary layer. Results are displayed as profiles and histograms of C_n² and (epsilon) for daytime, near sunset, and nighttime conditions.

Heterodyne CO₂ Doppler lidar measurements of horizontal wind velocity from the surface to 11,000 feet AGL using the Velocity Azimuth Display (VAD) method were made at Holloman AFB, NM from the end of July through mid-August 1998. These data were entered real-time into the space maneuver vehicle descent analysis program to make flight performance predictions needed for test decisions. Daily measurements encompassed the early morning time period associated with the stably-stratified nocturnal boundary layer (NBL). Measurement periods were characterized by growth the decay of wind maxima or jets at different altitudes. Strong vertical shears were often observed in conjunction with these wind maxima. Relative backscatter profiles at the lowest altitudes exhibited periodic oscillations on most mornings. Relative backscatter profiles at the lowest altitudes exhibited periodic oscillations on most mornings. The observed NBL wind profiles were poorly represented by the Ekman model.

We comment on the new atmospheric metrology experiments conducted in support of ABLACT. We will present the results from a wind-scintillometer experiment and show the most recent transverse coherence length and isoplanatic angle data from a new Atmospheric Turbulence Measurement and Observation System (ATMOS). The results from the wind scintillometer are inconclusive, and we suggest possible explanations and improvements. The ATMOS data provides a promising short-term characterization of North Oscura Peak. In addition, we address the ability to predict r_o from the local wind speeds.

High-bandwidth measurements of atmospheric velocity and temperature fluctuations in the high troposphere/low stratosphere using aircraft-based hot-wire anemometers requires calibration. An in-situ calibration characterizing wire sensitivity at high subsonic Mach numbers and relatively low temperatures and pressures was performed. Custom designed constant-temperature and constant-current anemometer equipment has been used for these atmospheric measurements. Two sets of calibration experiments are described, one in a controlled laboratory environment where the Mach number and temperature were varied and the other on board a C-135E aircraft. The aircraft test were conducted by varying the flight Mach number at different pressure altitudes while flying into an upper-level low pressure area, achieving variability in velocity, temperature, and pressure. Results obtained indicate increased sensitivity to velocity while operating the wire at a low overheat ratio. The calibration data was fit to a form of King's law which was found to work well for in-situ calibrations.

We report concurrent ground-based scintillator/airborne constant-current anemometer (CCA) measurements made along a 51.4 km-long slant path between Salinas and North Oscura peaks, NM. Simultaneous path-averaged refractive index structure parameter (C_n²) measurements from the CCA and the scintillometer show good agreement, with deviations apparently due to localized effects of underlying topography and metrology. Statistics from both data sets are presented in the form of histograms and cumulative distribution functions. CCA C_n² point measurements are compared to underlying surface topography. We discuss possible effects of instruments anomalies, analysis methods, and atmospheric velocity fluctuation levels. We present conclusions and made recommendations for future similar experimental efforts.

A six-year data set of refractive index structure parameter (C_n²) results from VHF radar observations at White Sands Missile Range, NM is used to calculate slant path values of the transverse coherence length (r_o), the isoplanatic angle, and the Rytov variance. The calculations were for a spherical wave condition, a wavelength of 1 micrometers , four different elevation angles, two path lengths, and platform, such as an aircraft, at 12.5 km MSL. Over 281,000 radar-derived profiles sampled at three minute intervals with 150-m height resolution were used for the calculations. The approach, an 'onion skin' model, assumes horizontal stationarity over each entire propagation path and is consistent with Taylor's hypothesis. Refractivity turbulent effects are greatly reduced as the elevation angle increase, a pronounced seasonal effect is seen consistent with climatological variables and gravity wave activity, and interactions of enhanced turbulence in the tropopause region is evaluated. An evaluation of inner scale on the calculations is discussed. Results of a two region model understood in terms of upward propagating gravity waves that are launched by strong winds over complex terrain are shown.

The Starfire Optical Range has measured stellar scintillation to 0.9 to 1.7 microns over a wide range of elevation angles. The telescope pupil was imaged on to a mask with four circular aperture of scaled diameters 0.1, 0.2, 0.75 and 1.5 m. These smaller pupils were then re- imaged onto InGaAs photodiodes operating at 10 kHz. The entire 3.5m pupil was also imaged onto a fifth photodiode. Since all five signals were recorded simultaneously, the influence of aperture diameter on scintillation statistics can be readily seen. The detectors were located at pupil planes; no fluctuations due to atmospheric tilt were measured. Comparisons of power spectral densities, signal variances and other fluctuation statistics have been made as functions of the aperture diameter and elevation angle. Experimental results and theoretical expectations reveal widespread agreement. Within experimental error, log-normal statistics are followed. High spatial frequency content increased with elevation angle. Aperture averaging of scintillation variance followed a 7/6th dependence. Increasing the aperture dimensions had an even larger effect on the number of fluctuations below a given threshold. Scintillation in the near-IR has been shown to produce consistent result with previous studies performed at visible wavelengths.

We report simultaneous balloon-borne thermosonde/airborne constant-current anemometer measurements made over a portion of White Sands Missile Range, NM. For the first time, vertical profiles of the refractive index structure parameter (C_n²) data generated from shallow slant aircraft flight paths are compared to the balloons vertical C_n² distributions. We discuss possible adverse effects of meteorology and atmospheric velocity fluctuations. We present conclusions and make recommendations for future similar experimental efforts.

The measurement sensitivity of CO₂ differential absorption lidar (DIAL) can be affected by a number of different processes. We have previously developed a Huygens- Fresnel wave optics propagation code to simulate the effects of tow of these processes: effects caused by beam propagation through atmospheric optical turbulence and effects caused by reflective speckle. Atmospheric optical turbulence affects the beam distribution of energy and phase on target. These effects include beam spreading, beam wander and scintillation which can result in increased shot-to-shot signal noise. In addition, reflective speckle alone has been shown to have a major impact on the sensitivity of CO₂ DiAL. However, in real DiAL systems it is a combination of these phenomena, the interaction of atmospheric optical turbulence and reflective speckle, that influences the results. The performance of our modified code with respect to experimental measurements affected by atmospheric optical turbulence and reflective speckle is examined. The results of computer simulations are directly compared with lidar measurements. The limitations of our model are also discussed. In addition, studies have been performed to determine the importance of key parameters in the simulation. The result of these studies and their impact on the overall results will be presented.

The Absolute Radiometric Code (ARC) is a collection of Matlab functions tied together under a Matlab Graphical User Interface (GUI). ARC was developed as part of the Satellite Imaging Experiment conducted by the Air Force Research Laboratory at Kirtland, AFB, in order to get fast estimates of the Optical Cross Sections of various satellites. ARC uses multiple star measures to calculate the atmospheric and optical transmission of the system. The transmissions are then used to compute the optical cross section of an object. Generally, the optical transmission of a sensor system can be characterized quite well, so it serves as a sanity check on all ARC results. The atmospheric transmission changes considerably from night to night and even from hour to hour on the same night. ARC uses a collection of calibration stars at various elevation angles to determine the atmospheric transmission through the viewing times. The star calibration is generally taken several times during the experiment period.

A model of irradiance fluctuations for a propagating optical wave in a weakly inhomogeneous medium is developed here under the assumption that small-scale irradiance fluctuations are modulated by large-scale irradiance fluctuations of the wave. The resulting scintillation index from this theory has the form (sigma) ₁² equals (sigma) _x² + (sigma) _y² + (sigma) _x² (sigma) _y² where (sigma) _x² denotes large-scale scintillation and (sigma) _y² denotes small-scale scintillation. By applying a modification of the Rytov method that incorporates an amplitude spatial frequency filter function under strong fluctuation conditions, tractable expression are developed for the scintillation index of a Gaussian beam wave that are valid under moderate- to-strong irradiance fluctuations. The expected scintillation of Gaussian beams predicted by these analytic models is compared to the experimental data previously published.

ABLSim is a software tool for high fidelity modeling of advanced optical systems such as a laser weapons systems and compensated imaging syste. It makes use of a well established modeling approach known as 'wave optics', in which optical wavefronts are modeled using 2D meshes of complex numbers. Wave optics is the most powerful approach known for predicting the performance of optical systems in the presence of strong turbulence. ABLSim differs from previous wave optics modeling tools primarily in that it is much easier to use. Historically, wave optics codes been notoriously difficult to use with the result that only a very small number of people - the code authors and a few others -could use the codes effectively. ABLSim is designed to make wave optics accessible to a much broader user community. In ABLSim, the user assembles system models in a 'connect-the-blocks' visual programming environment, where each block represents a system component such as an optical sensor, a laser source, a mirror or a lens. Each connection represents a specific type of interaction: for example, connections between optical components represent optical interfaces. ABLSim provides a GUI for setting up parameter studies and a Matlab interface for postprocessing.

Optical systems which transmit power density optical radiation present real design and implementation challenges. Sophisticated multi-disciplinary methods have been developed to support the design and analysis of the interaction of the optical radiation field and the transmissive and reflective optics which the field interacts with. The primary effect which results are distributed thermal deformation of the optical surfaces resulting in undesirable aberrations, loss of Strehl and beam 'quality'. Modern optical systems involve the use of adaptive optical systems which mitigate the effect of these aberrations within their spatial and temporal correction bandwidths. The authors have been involved in a study, which addresses the closed loop correction of thermally induced beam train aberrations using computational numerical models to describe the wavefront effects. This paper reports on the analysis methods used and describes some preliminary results.

The ABL Lockheed Martin has prepared and validated a highly versatile adaptive optics testbed to simulate in an accurately scaled fashion all aspects of ABL laser beam propagation, including atmospheric compensation and pointing and tracking in selected atmospheres. This system allows repetitive, highly controlled, and well diagnosed experiments to be carried out that are generally impossible to do in field test where the user has little control over atmospheric and other test conditions. Testing of beam control hardware including components, assemblies, control loops and software, as well as development of methodology such as alignment and sensor techniques, determinations of system operational robustness, and finally, measurement of overall system performance under various atmospheric or other propagation and seeing conditions are routinely done. This presentation will discuss 1) the system scaling chosen to preserve diffraction, turbulence and temporal fidelity to ABL, 2) agreement of experiment results to those of other laser propagation experiments and wave optic code simulations, and 3) experiments that have demonstrated ABL beam control system robustness, compensation for jitter and turbulence, and overall performance when operating in atmospheric turbulence that emulates that measured in the real-world theater.

The Airborne Laser Advanced Concepts Testbed (ABL ACT) is a low power beam control test facility located at the northern end of White Sands Missile Range atop North Oscura Peak. The purpose of ABL ACT is to explore concepts for laser propagation under high scintillation conditions. This paper gives an updated overview ofthe facility, reviews data collected to date, and details future plans

The mission of the HABE is to resolve critical acquisition, tracking, and pointing (ATP) and fire control issues, validate enabling technologies, simulations, and models, and acquire supporting data for future space-based lasers experiments. HABE is integrating components from existing technologies into a payload that can autonomously acquire, track, and point a low power laser at a ballistic missile in its boost phase of flight. For its primary mission the payload will be flown multiple times to an altitude of 85,000 feet above the White Sands Missile Range. From the near-space environment of the balloon flight, HABE will demonstrate the ATP functions required for a space-based laser in a ballistic missile defense role. The HABE platform includes coarse and fine gimbal pointing, IR and visible passive tracking, active fine tracking, internal auto- alignment and boresighting,and precision line-of-sight stabilization functions. This paper presents an overview and status of the HABE program.

The ABL Beam Control design incorporates Common Path/Common Mode (CP/CM) architecture because it provides many important operational features, without which the system would have difficulty performing well in the stressing military environment. These features include 1) tolerance for optical misalignment, 2) elimination of the need for boresighting, 3) graceful degradation, 4) correct accounting for all optical path disturbances, 5) relaxed tolerances of optics, and 6) compensation for thermal disturbances. The concept for CP/CM operation, both in wavefront compensation and in automatic self-alignment and pointing, will be given. Experimental and simulation data will demonstrate the effectiveness of the CP/CM ABL approach.

In the conventional approach to active tracking, the target is illuminated by an illuminator laser and the backscatter is collected to produce an image for the tracker. Atmospheric turbulence, especially when it is distributed over the entire propagation path, produces intensity scintillation of the illuminator laser beam. This scintillation reduces the uniformity of target illumination and degrades tracker performance. With multibeam laser illumination the single illuminator is replaced by several, mutually incoherent illuminator beams. The multibeam approach produces a more uniform target image and improves tracker performance. In this paper, we describe the design of a multibeam illuminator capable of producing up to nine beams. We discuss characterization test performed across the 5.4-km propagation range at the Lincoln Laboratory Firepond facility.

We have constructed a target-board platform to provide adaptive-optics and tracking performance characterization for the Airborne Laser Advanced Concepts Testbed program. The target board comprises 1536 discrete sensors distributed over a 1-meter by 2.5-meter array mounted to the side of a specially modified Cessna Caravan aircraft. The aircraft platform includes multiple beacon sources for adaptive- optics and tracking, a large-capacity data-recording system and a real-time telemetry ground-link for data display. In this paper we provide an overview of the target-board platform. We discuss the results of requirements analysis for target-board detector configuration, and describe the detailed design and capabilities of the various sub-systems.

The Airborne Laser (ABL) program requires a large aperture, highly transparent window to allow the high energy laser beam to be focused on targets. This window presents many challenges as it is thin, large in diameter and very highly curved. Additionally, the window must be made from a material highly transparent at 1.315 micrometers, the chemical oxygen-iodine laser wavelength, have good transmission from the visible through 3 micrometers and be able to withstand the rigors of operations on a tactical aircraft. To manufacture this window, a unique partnership between two companies, Heraeus and Corning, was forged to demonstrate the process and manufacture the window blanks. Infrasil 302, a Heraeus product, is the only material with low absorption at 1.31 micrometers that can be produced in large enough quantities to make a window blank of the required size. Corning has developed the technology to flow- out and sag glass products to make highly curved optics without the need to machine them out of a cylindrical block. Using their experience and a common desire to support the ABL program, the two companies worked together to develop the processes that produce the window blanks. Contraves Brashear Systems of Pittsburgh will polish the blank in to its final form, with coatings applied by Optical Coating Laboratories, Inc. of Santa Rosa to maximize transmission.

Tracking through a turbulent atmosphere has several challenges. If the target is extended, such as a large target being illuminated with laser energy from the tracking aperture, the problems of scintillation and anisoplanatism cause significant concerns. The 'blotches' caused by scintillation can be interpreted by the tracking algorithms as tilt and incorrectly applied to the steering mirror. Similarly, anisoplanatism imparts tilt components from separated points, that may be independent, and not act as coherent tilt that is possible to correct with one mirror. The authors have been involved in a study that compares the performance of 14 different tracking algorithms under scintillated conditions. Image data, available from Lincoln Laboratory, has been used to calculate tilt from the different algorithms and do comparisons using Power Spectral Density analysis. The results show that different algorithms have significantly different performance characteristics.

The problem of suppressing acoustically induced vibration in precision equipment is addressed. The study specifically addresses acoustically induced vibration in an airborne optical train. Two approaches were studied. The first approach is to inertially instrument each optical element, sensing the motion causing optical jitter. The array of vibration measurements is used with a robust feedback control law and with an adaptive feed forward algorithm to precisely cancel the optical jitter. The second approach is to adapt an SVS active sound barrier concept to the airborne problem. The active sound barrier uses a combination of feed back and adaptive feed forward control to attenuate the sound passing through the barrier. Both approaches were demonstrated in a laboratory experiment to have excellent performance. Using the inertial instrument approach, jitter was reduced by as much as a factor of 43. Using the active sound barrier, an acoustic reduction of 17 dB was demonstrated. Anticipated benefits include improved performance for ABL weapons used for theater ballistic missile defense. This experiment was funded through an SBIR Phase I contract, AF Contract No. F29601-95-C-0116, SBIR Topic AF95-113. The experimental set up and the results will be described.

Before fine tracking algorithms can be evaluated for performance at the ABL-ACT facility at North Oscura Peak, the image needs to get onto the fine track sensor. This requires interaction between the gimbal controller, course tracker, and the fine tracker. In order to develop this hardware for North Oscura Peak, and to meet the proposed schedule, a local facility was required. NuSord was developed for this purpose. In addition to supporting the buildup, NuSord will assist in the integration of future hardware and software system that would eventually end up at NOP.

Tracking through a turbulent atmosphere involves many challenges. In the pursuit of better tracking techniques Gemini, a dual tracker was developed. Intended as a research too, Gemini can be used to characterize anisoplanatism, wind, and other atmospheric effects on a frame by frame basis. In addition, one tracker can be converted to a pupil plane or wavefront sensor.

The implementation of an incremental optical encoder for measurement of gimbal pointing angles is discussed. The application described is typical of many programs being conducted at SVS Systems, Inc. Performance requirements such as resolution, accuracy, bandwidth, size, and weight are described and the advantages of using the optical encoder instead of more 'traditional' technologies are given. The resolution of the optical encoders is on the order of 20 nanoradians. Disadvantages to using the optical incremental encoders are discussed as implementation challenges. An overview of how these challenges were overcome is described. A control system implementation using the encoders for gimbal stabilization is presented, including simulations result. The combination of resolution, repeatability, and accuracy of the encoders opens new possibilities for gimbal stabilization without rate sensors attached to the pointing mirror, as shown through simulation. Test results verifying the proper operation of the encoder are presented.

The ABL Acquisition, Tracking, Pointing and Fire Control systems functions are described. The key to the design process is a detailed situation that models the controls, algorithms, engagement sequence, mode logic, passive track sensors, active track sensor, plume phenomenology, active return from the target, and the effects of atmosphere. The application of the simulation to the design process is described, including passive track, active track, and kill assessment. Two field tests used to validate the simulation are briefly described.

In the Airborne Laser program, a portion of the Fire Control ground and flight code is being automatically generated from a Matlab, Simulink simulation environment. In this paper, the Fire Control process is briefly described and the ABL Fire Control simulation is described. The Matlab Code Gen tool for automatically generating C code from the Simulink simulation is described. A set of the Fire Control algorithms was selected to be developed using the Code Gen approach. The software standards for Code Gen developed code are described and the software metrics status is provided.

An account of the recently completed, 1-1/2 year ABL risk reduction deformable mirror (DM) program will be given. In this effort, candidate sub-scale deformable mirrors (SSDM) supplied by tow vendors were tested for manufacture and performance quality. The down-selected mirror was then provided with a newly-developed, high performance, multiple wavelength, low stress, very low absorptance faceplate optical coating. The SSDM was then operated for cycle number and stroke, and under high laser flux, that exceeds the operational requirements of the ABL DMs. The successful results for these tests, carried out with the contributions of a multifaceted integrated product team, will be reported.

This paper develops an infinite dimensional theory for filtering and control in the presence of non-rational spectra. It begins with a review of the original work of A.V. Balakrishnan for the continues time case. This work formulates an auxiliary state space signal model for the case of non-rational spectra. The result is the recovery of Kalman like signal generation models with the resulting separation principle for control. New results, based on unpublished notes of Balakrishnan, on discretization of the model are developed. Although the results can and will be generalized, this paper only covers the 1D theory.

This paper concerns a class of adaptive optics problems in which phase distortions due to atmospheric turbulence are corrected by adaptive wavefront reconstruction with a deformable mirror - i.e., the control loop that drives the mirror adapts in real time to time-varying atmospheric conditions, as opposed to the linear time-invariant control loops use din conventional 'adaptive optics.' The basic problem is posed here as an adaptive disturbance rejection problem with many channels. The solution given here is to augment a linear time-invariant feedback control loop with an adaptive feedforward control loop based on a multichannel adaptive lattice filter. Simulation results are presented for a one-meter telescope with both single-layer and two- layer atmospheric turbulence profiles. These results demonstrate the significant improvement in imagin resolution produced by the adaptive control loop.

Finite turbulence outer scale attenuates turbulence power at low spatial frequencies, providing a finite variance for turbulence-induced phase. The temporal properties of low spatial-frequency aberrations such as tilt are affected directly by finite outer scale turbulence models. When optical estimation techniques are used in beam-steering applications, the estimator form and its performance are related directly to the correlative properties of tilt and higher-order modes as determined by the value of Lo/D. In this work, we consider the effect of finite turbulence outer scale on the performance of optical tilt compensation incorporating time-delayed tilt plus higher-order modes. The results indicate that while smaller values of Lo/D provide for higher Strehl ratios after tilt compensation, the Strehl ratio gain obtained through optimal compensation is reduced with decreasing values of Lo/D. For the relative aperture diameter D/r₀ equals 5 and using time-delayed tilt plus higher-order modes through Zernike 15, the Strehl ratio gain with time delay vr/D equals 0.5 is approximately 15 for L₀D equals 100. Under the same conditions, the Strehl ratio gain for L₀D equals 2 is approximately 3.

In optics, Zernike orthogonal polynomials are used as a basis set for the expansion of wavefront phases. Due to the atmospheric turbulence-induced stochastic nature of the underlying process involved, the spatial-temporal correlation functions of the Zernike polynomial phase expansion coefficients must be evaluated if adaptive optics is to be employed. In this paper, these correlation functions are developed using a layered atmospheric model and calculations for the first few low-order Zernike modes are performed. Using these correlation functions, an underlying linear dynamical system is identified. Within an acceptable error bound, the correlation functions of this system are representative of the calculated correlation functions. This syste, in turn, provides the basis for the employment of advanced control and estimation concepts in an adaptive optics system that is being developed for the ABL.

A laser beam propagating in the atmosphere are influenced simultaneously by thermal blooming and turbulence that results in aberrations of a focal spot. Character of thermal blooming depends not only on atmospheric conditions but also on beam power and velocity of a target. Turbulent aberrations prevail at large sped of scanning, from this point of view they are more important. In the previous papers it was pointed out that thermal aberrations of laser beams decrease sharply as the object velocity increases. If Mach number is greater than unity and laser power is not too great, the influence of thermal blooming is negligible. Effectiveness of phase correction for thermal blooming increases at increase of scanning velocity, because in this case the thermal lens is placed near the transmitting aperture. On the contrary, effectiveness of correction for turbulent aberrations decreases when the object velocity increases. Turbulent aberrations do not depend on sped of angular scanning but in the case of a moving object the requirements to the adaptive system bandwidth are higher than that for a motionless target. For beams with power about 500 kW and wavelength (lambda) equals 1.315 micrometers on the upper atmosphere paths turbulent aberrations are always stronger compared to thermal blooming even for motionless targets. So if the correction for turbulent aberrations is possible, the correction for thermal blooming is possible too.

A new doubly stochastic probability distribution function (PDF), namely the two parameter gamma-gamma distribution, is developed to describe the intensity fluctuations of a laser beam propagating through turbulent media. The lognormal distribution is the traditional governing distribution in the weak region; however in strong turbulence the intensity of a laser beam is better described by Beckman's PDF and lognormal modified PDF. It is shown in this analysis that the gamma-gamma PDFs in the strong region. The gamma-gamma PDF is compared here with recently published simulation data over a range of atmospheric conditions. Although the parameters of the gamma-gamma PDF are determined based on best fitted curves, the purpose of this analysis is to explore the existence of such a universal PDF. Unlike all other models, the gamma-gamma has a closed form CDF, making it of extreme importance for real time calculations.