This PDF file contains the front matter associated with SPIE Proceedings Volume 7476, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Air-sea interaction processes play a dominant role with respect to detection ranges of shipborne radar and infrared sensor systems. Especially in the littoral most often temperature and humidity gradients affect propagation paths and are the reason for abnormal phenomena such as ducting or mirage. Besides refractivity, spray and aerosols ejected from the sea surface can further degrade the quality of shipborne surveillance systems. Thus environmental effects might seriously hamper ship self defense. During the Ligurian Air-Sea Interaction Experiment (LASIE '07 - 16.06.-26.06.2007) the Federal Armed Forces Underwater Acoustics and Marine Geophysics Research Institute (FWG) carried out simultaneous in-situ measurements of meteorological and oceanographic parameters to study air-sea interaction processes with respect to littoral boundary layer variability. The characterization of the environment included both, in-situ measurements of atmospheric and sea surface parameters. Investigations were carried out on board RV PLANET, RV URANIA and at the ODAS-Italy1 buoy of the Italian National Council of Research (CNR). On board RV PLANET the sea surface and meteorological conditions were analyzed by two multi-sensor buoys, ship sensors and radiosondes. Emphasis was given to the vertical structure of the Marine Boundary Layer (MBL) and its variability. It was analyzed by a one lense lidar ceilometer CL31, a tethersonde system TT12 and radiosondes RS92 (Vaisala). The latter were launched every three hours. The TT12 consisted of three radiosondes, which could be adapted to separate altitudes of special interest. The experiment was characterized by changing meteorological conditions resulting in offshore and onshore blowing winds. In the first case the air temperature TAir was higher than the sea surface temperature TWater leading to a very stable surface layer. This situation was associated with a strong temperature inversion and a very clear atmosphere with a visibility of about 70 km. The second case (T_Air<T_Water) was dominated by convection processes and a pronounced aerosol production. Good correlation was found for the Mixing Layer Height (MLH) by the lidar ceilometer and the radio soundings.

Propagation in the maritime boundary layer is determined by the refractive index of the atmosphere above the sea. The refractivity is determined by a set of parameters, which characterize the atmosphere and the underlying medium, the sea surface. During experimental RCS measurements of ships the measured RCS is dependent on the actual propagation properties. To deduce calibrated and valid data these have to be taken into account. A simulation package was developed using the parabolic equation model TERPEM and the CAD based RCS simulation tool CADRCS which are merged to a general RCS model NAVRCS. The contribution describes the philosophy of the approach and discusses typical simulation results, which are compared with validation measurements.

A ship's exhaust gas contains both hot gas molecules, which emit infrared radiation at specific wavelengths (line emitters), and soot particles which emit broad-banded, like a black body. Our modeling shows that the observed radiance from these emissions falls at different rates with distance. The attenuation of intensity is caused by absorption and scattering of the emitted radiation in the atmosphere. The hottest part of the exhaust plume is spatially confined to a relative small volume. Usually, a ship's hull and its superstructure have a higher temperature than the sky or sea background. The temperature difference is generally not very large. However, the ship has a spatial extent that is much larger than the plume's. In this work we study how both the emitted radiation from the plume and the ship's total signature decrease with increasing distance. This study is based on experimental data that was collected during a measurement campaign at the southwest coast of Norway. Shore-based digital IR cameras, both LWIR and MWIR, recorded image sequences of ships as they sailed away from close to shore (~ 1 km) in a zigzag pattern out to about 10 km. We used a statistical method to identify the gas cloud pixels and used their integrated radiance as a measure for the plume intensity. The ship signature is defined here as the integrated radiance over all the ship's pixels in the imagery. From infrared spectroscopic data, collected using a Fourier Transform Infrared spectrometer aimed at the ship's plume when the ship is close to shore, a model is obtained for the composition of the exhaust gas. This model was used to perform FASCODE simulations to study numerically the attenuation with distance of the plume radiance. Our work shows that this approach may be well suited to explain the observed signal decay rate with distance.

Propagation of electromagnetic waves through canopies of wood are of interest for he choice of operating frequencies for microwave based sensors of different kind. It is known that in general the propagation properties become worse with higher frequency. Especially the upper millimeterwave bands are severely attenuated by leaves. Measurements were conducted during a period in spring on a transmission path through an apple tree. The measurement period covered states of the tree ranging from leave-less over blooming to fully developed leaves on the branches. Three frequency bands were covered, namely 10 GHz, 35 GHz and 94 GHz. To allow a concise judgment of the data, meteorological measurements were done in parallel.

Between the wavelengths of the visible and the Short Wave Infrared (SWIR), the glow of the sky from chemical radiance and absorption changes dramatically. Thus too, the structure and appearance of clouds change. By directly and simultaneously examining clouds in an urban and a rural setting, we investigate the correlation between the appearance of clouds present in the SWIR, NIR, and visible. The experimental setup consists of two sensors, one a NIR to SWIR sensitive InGaAs array, and the other a visible CCD, both co-located on an AZ-EL mount, and both co-boresighted so that different viewing angles of the sky are possible. The SWIR sensor is sensitive from 0.9 μm to 1.7 μm. The CCD sensor collects cloud images in the visible region. By making corrections for focal length and pixel size, the visible and SWIR data can be compared. After taking several nights of data in the urban environment of Albuquerque, NM, the entire system was then re-located to a rural location in southern New Mexico.

The impact of atmospheric turbulence in the marine boundary layer on the performance of ship-borne and coastal optical and infrared surveillance sensors is well known. On the one hand, the detection process may benefit from scintillation of signals from point-like targets at long range, while target identification is hampered by turbulence induced blurring and beam wander. According to the commonly used turbulence model, based on the Monin-Obukhov similarity theory for the marine boundary layer (the so-called bulk model), the structure function for refractive index C_n² decreases with altitude. This height dependence of C_n ² and the associated blurring, scintillation and beam wander, has consequences for the range performance of sensors against incoming small targets. In the paper, predictions of the height-dependence of turbulence, based upon the bulk model, will be given for a number of scenarios from previous measurement campaigns, such as POLLEX and SAPPHIRE. In these experiments, taking place in a variety of weather conditions (e.g. Air-Sea Temperature Difference (ASTD)), images were collected from vertical arrays of sources at long range. In addition imagery was collected of helicopters, acting as point-targets at ranges up-to more than 30 km. The imagery is used to determine turbulence effects, which are compared with the model predictions. The results of this comparison, showing details on the validity of the model, are presented in the paper.

Recent advances in low-cost high power diode lasers have made available a new type of illuminator source for LADAR remote sensing systems. These sources tend to be smaller more rugged, and have better power conversion efficiency than more conventional pumped crystal solid state lasers. They can be run in short pulse or long pulse modes with pulse repetitions from DC to 10s of kilohertz. Although they don't have the peak power of a Q-switched laser, they make up for it in higher average power. They also tend to have large optical band widths. These factors make them well suited to direct detection, as opposed to coherent detection, since the lower source coherence reduces detrimental atmospheric effects related to speckle noise and scintillation of the outgoing beam. In this paper we discuss these effects and situations where diode lasers provide an advantage when working through long slant paths. Laboratory measurements are presented to illustrate the image improvement using less coherent diode lasers for imaging LADARs.

The method is proposed in order to model the propagation of a laser beam through turbulence. Two kinds of beams are under consideration: (i) beams of small power; (ii) high-power beams with effect of self-focusing (including ultra-short laser pulses). Turbulent atmosphere can be modeled with the aid of the full Navier-Stokes equations. As known, turbulent fluctuations decay in isolated system due to dissipation. To prevent decay, energy transfer from outside must exist. So we introduced an additional term into the equation of energy. The amplitude of arising disturbances has been investigated. The Navier-Stokes equations were reduced to integral ones and solved by iterative procedure. The comparison of the subsequent iterations demonstrates rapid convergence. The nonlinear solution has an important feature: the dispersion law depends on coordinates and time. The range of applicability of the numerical method has no restrictions on the value of the Reynolds number. Turbulent properties can be found by averaging over initial data. Some theoretical results were confirmed by experiments relating to grid turbulence. We have also considered the 3D objecttargeting problem. Some examples are given.

The Differential Image Motion Monitor (DIMM) is a standard and widely used instrument for astronomical seeing measurements. The seeing values are estimated from the variance of the differential image motion over two equal small pupils some distance apart. The twin pupils are usually cut in a mask on the entrance pupil of the telescope. As a differential method, it has the advantage of being immune to tracking errors, eliminating erratic motion of the telescope. The Differential Laser Tracking Motion (DLTM) is introduced here inspired by the same idea. Two identical laser beams are propagated through a path of air in turbulent motion, at the end of it their wander is registered by two position sensitive detectors-at a count of 800 samples per second. Time series generated from the difference of the pair of centroid laser beam coordinates is then analyzed using the multifractal detrended fluctuation analysis. Measurements were performed at the laboratory with synthetic turbulence: changing the relative separation of the beams for different turbulent regimes. The dependence, with respect to these parameters, and the robustness of our estimators is compared with the non-differential method. This method is an improvement with respect to previous approaches that study the beam wandering.

The proper characterization of the turbulence structure in an astronomical site requires a statistical analysis of the refractive index structure constant, C_N²(h). Our team has been monitoring this variable since November 2002 at the Teide Observatory (Tenerife, Canary Islands, Spain). We have derived the seasonal evolution of turbulence structure at this site using data from more than 150 nights of useful G-SCIDAR measurements. The monthly statistical profiles for different years present a similar structure for different years, suggesting a stable seasonal evolution of the turbulence at the Canary Islands sites. From this statistical analysis, we have derived the seasonal evolution of the Fried's parameter, the isoplanatic angle and the coherence time. The average values for these parameters are < r₀ >=15.1±4.6 cm, <θ₀ >= 2.7±1.3 arcsec and <τ₀ >= 5.8 ± 3.1 ms. Uncertainties indicate the standard deviation of the averaged measurements. These statistical values for atmospheric adaptive optics parameters and their smooth seasonal behavior bring up the sky quality of the Canary Islands astronomical sites for the implementation of adaptive optics systems.

The development of adaptive optics systems for projects related to large telescopes demands a proper knowledge of the atmospheric turbulence. Due to the lack of long-term information on optical turbulence, high-altitude winds (in particular winds at the 200-mbar pressure level) were adopted as a parameter for estimating the total turbulence at a particular site, since there are large wind databases spanning for several decades. On-site measurements of C_N²(h) profiles (more than 20200 turbulence profiles) from G-SCIDAR observations and wind vertical profiles from balloons have been used tocalculate the seeing, the isoplanatic angle and the coherence time for the Teide Observatory (Canary Islands, Spain). The connection of these parameters to wind speeds at ground and 200-mbar pressure level have been studied and discussed.

We present a novel method for integrating a wavefront sensor into a deformable mirror. This development should simplify the design of laser and electro-optic systems, and lead to smart mirrors which need no external control systems. In operation, a small fraction of the incident light is transmitted through the mirror coating and is sampled by a Hartmann Mask. Options include open loop, traditional closed loop or fully integrated operation whereby the wavefront sensor is used to provide direct feedback to the mirror actuators, enabling automatic alignment or phase conjugation.

The Zonal Bimorph Deformable Mirror (ZBDM) is a new concept of adaptive mirror. It exploits the benefits normally associated with bimorph mirrors, namely simple rugged construction, low capacitance, and cost effectiveness, but in a significant departure from classical, edge supported bimorphs each element is supported from underneath. This results in a localized (zonal) response that should enable the device to be scaled up to large aperture, multi-1000 element devices. Crucially, the combination of continuous support coupled with the use of flexi-circuit interconnect promotes the assembly of a high density 'tweeter' onto a lower density, high dynamic range 'woofer' to generate an integrated, dualstage deformable mirror which can deliver both high resolution and high dynamic range simultaneously. Such a device has the potential to significantly simplify the design of AO systems. We present the progress made on the development of the ZBDM as part of a collaborative programme funded by the UK Science and Technology Facilities Council.

We describe two types of adaptive optics systems developed at FGAN-FOM and the progress in their realization during the last year will be presented. The first system is based on classical adaptive optics scheme and is aimed to resolve objects inside the isoplanatic angle of the wavefront sensor. The second system is based on an iterative algorithm and on the evaluation of the quality of the image to correct the wavefront. This last system is intended to resolve extended targets outside the isoplanatic limits. A constructed mobile system will be also introduced as multipurpose system for measuring atmospheric characteristics as well as tracking and resolving point-like sources in the isoplanatic angle. Finally some results of measurements and attempts to correct the centroid movement of the image of an incoherent point source located at 2.5 km distance using the mobile system will be discussed.

A wavefront sensor which takes advantage of the moire deflectometry has been constructed for measuring atmosphere induced wavefront distortions. In this sensor a collimated laser beam propagates through turbulent atmosphere, then a beam splitter splits it into two beams and the beams pass through a pair of moire deflectometers. Directions of the grating's rulings are parallel in each moire deflectometer but are perpendicular in the two beams. Using a suitable array of lenses and mirrors two sets of moire patterns are projected on a CCD camera. A suitable spatial filter removes the unwanted frequencies. Recording the successive moire patterns by the CCD camera and feeding them to a computer, allow temporal fluctuations of the laser beam wavefront phase to be measured highly accurately. Displacements of the moire fringes in the recorded patterns correspond to the fluctuations of two orthogonal components of the angle of arrival (AA) across the wavefront. The fluctuations have been deduced in successive frames, and then evolution of the wavefront shape is determined. The implementation of the technique is straightforward and it overcomes some of the technical difficulties of the Schlieren and Shack-Hartmann techniques. The sensitivity of detection is adjustable by merely changing the distance between two gratings in both moire deflectometers and relative grating ruling orientation. This overcomes the deficiency of the Shack-Hartman sensors in that these require expensive retrofitting to change sensitivity. Besides, in the moire deflectometry, the measurement is relatively insensitive to the alignment of the beam into the device. Hence this setup has a very good potential for adaptive optics applications in astronomy. Since tilts are measured in the Shack-Hartmann method at discrete locations, it cannot detect discontinuous steps in the wavefront. By this method discontinuous steps in the wavefront are detectable, because AA fluctuations are measured across the wavefront.

The known that the wave-front sensor is one of the most important element of adaptive optical system. Certainly that type of the wave-front sensor and its parameters hang from type used reference radiation (source) [1]. Particularly follows to distinguish using coherent and incoherent reference source. In this report will is described designs and algorithms of the work two sensors, first, working with coherent, and second one, with incoherent radiation. Possibilities of constructing a wave-front sensor for the adaptive system in the Big Solar Vacuum Telescope are considered. A modified correlation tracker (MCT) is proposed. The sensor is tested by measuring the displacement of the image of the solar granulation pattern in the first and second foci of the telescope under clear vision conditions.

Simple analytical expressions for parameter Strehl of ground-based astronomical telescope: (i) without adaptive correction, (ii) phase correction with use single laser guide star, (iii) phase correction with use multi-guide stars (square matrix system of guide stars with variable number of elements) are obtained. Models of the vertical dependence of the structure parameter of refractive index of the turbulent atmosphere for various sites are used in the calculations. Modal phase correction is considered to large aperture ground-based telescope with multi-guide stars. Wave aberrations presented in the in terms of Zernike polynomials are used to calculate the angular correlation of modal components of phase fluctuations of optical radiation propagating in the turbulent atmosphere. The size of the isoplanatic area in an adaptive optical system is studied. The influence of the model of vertical profile of the structure parameter of atmospheric refractive index fluctuations, the outer scale of atmospheric turbulence, and the size of receiving aperture of a telescopic system are analyzed. Requirements on bandwidth of adaptive optical system for effective correction are formulated.

An optical vortex, which possesses positive or negative topological charge, can be used as an information carrier in a free-space optical communication system because its special properties. By detecting the vortex with a Shack- Hartmann wavefront sensor, one can extract the information transferred by a vortex beam. However, additional optical vortices can spontaneously appear in the beam propagating over a long distance in the atmosphere or through a strongly turbulent medium. As a result, the vortex beam will contain a significant number of new vortices besides the initial one in the system receiving aperture. This may destroy the information carried by the initial vortex. In the paper, we will describe the reliability of detecting vortex with a Shack-Hartmann wavefront sensor in a scintillated vortex beam. The initial vortex can be detected even if the beam is strongly scintillated and with numerous newly emerged vortices. Numerical simulations and statistics show that the information can still be accurately interpreted to a certain extent from a vortex beam propagating through weak-to-strong atmospheric turbulence.

Phase singularities have been shown to cause one of the major problems for adaptive optics (AO) systems which attempt to correct for distortion caused by the atmosphere in line of sight free space optical communications over mid-to-long range horizontal paths. Phase singularities occur at intensity nulls in the cross-section of the laser beam at the receiver. When the light intensity drops to zero at these points the phase of the optical wavefront is undefined. Phase singularities occur in pairs of opposite sign (or rotation) and are joined by a wave dislocation, called a branch cut, with a corresponding 2π radian jump in the phase. It is this 2π jump which causes difficulties for common AO techniques. To negate the effect of the phase singularities they must be detected and then taken into account in the wavefront reconstruction. This is something not done by most of the zonal reconstruction algorithms commonly used in atmospheric turbulence correction. An experimental set up has been built and is used in the laboratory to examine the detection of phase singularities in atmospheric turbulence. This consists of a turbulence generator using a spatial light modulator (SLM) to mimic the atmosphere and a Shack-Hartmann wavefront sensor as the receiver. The branch point potential method for phase singularity detection is then implemented in post processing to locate the position of the phase singularities. Phase singularity detection can now be practiced under different conditions in a controlled manner. Some results of phase singularity detection from this experimental setup are shown.

In this paper we adopt a full density matrix treatment to deal with the interaction between long-pulse, circularly-polarized light and the sodium atoms. The time evolution curve of every 24 sub-state's population probability can be obtained by solving the Bloch equation of twenty-four hyperfine levels. We find that during the long pulse time(more than 100 ns), the final transition is only between the sub-level 3S_1/2 (2,2) and 3P_3/2 (3,3).What is more, the probability of the excited sub-state has become steady. Then we start the comparison between the 2-level model and the full density matrix method to show the rationality of rate equation and 2-level model for the long pulse, circularly-polarized light. We prove the rationality upon adopting 2-level model to deal with interaction between long-pulse, circularly-polarized light and the sodium atoms and thus bring the convenience to solve the interaction. Key words: Sodium beacon, long pulse, circularly polarized light, 2-level atoms, adaptive optics

In this paper we present an Adaptive Optics (AO) System properly developed for the fast automatic control of laser beam jitters on first and second order Hermite Gauss (HG) modes. This research has been driven by the necessity of suppressing laser beam geometrical fluctuations in the interferometric Gravitational Waves (GW) antennas. In fact, it is demonstrated that oscillations of higher order Hermite Gauss modes in the laser source couple with the interferometer asymmetries and give rise to additional noise that limits the antenna sensitivity below the value of 10^-23 1/square root of Hz. In the paper we demonstrate the feasibility of a novel AO System performing effective laser jitters suppression in the bandwidth up to 200 Hz. In particular we describe an innovative AO System that extracts error signals as HG coefficients and then corrects the wavefront through driver commands sent to the deformable mirror in terms of Zernike profiles. We have implemented and tested an experimental Prototype of the AO System in our laboratory at the University of Salerno. The results confirm effectiveness and robustness of the control which performs significant reduction of the first and second order laser beam geometrical fluctuations. In particular we have measured the decrease of astigmatism and defocus modes of 60 dB at low frequency below 1 Hz and of 20 dB up to 200 Hz, which at the best of the present technology fulfils the requirements for noise reduction of the interferometric GW detectors.