Impact of time-variant turbulence behavior on prediction for adaptive optics systems

For high-contrast imaging systems, the time delay is one of the major limiting factors for the performance of the extreme adaptive optics (AO) sub-system and, in turn, the final contrast. The time delay is due to the finite time needed to measure the incoming disturbance and then apply the correction. By predicting the behavior of the...

Using ultrasonic anemometers for temperature measurements and implications on Cn2

Investigation of optical turbulence from an unmanned aerial system

Wave propagation of electro-optical systems, lasers or imaging depends on the state of the atmosphere their beams are passing through. Fluctuations in the refractive index of air are responsible for signal attenuation and image degradation. This atmospheric effect is called optical turbulence and its strength is quantified by the structure...

Height dependence of characteristics of power spectra of temperature investigated in the surface layer of White Sands /US

A field trial was performed in the arid scrub area of White Sands, NM /USA in October 2017 investigating the atmospheric influence on imaging and sensor performance. In this paper we focus on the strength of optical turbulence. Optical turbulence is described by the structure function parameter of the refractive index Cn 2. It is responsible for...

Inhomogeneity of optical turbulence over False Bay (South Africa)

Atmospheric turbulence impacts on the propagation of electro-optical radiation. Typical manifestations of optical turbulence are scintillation (intensity fluctuations), beam wander and (for laser systems) reduction of beam quality. For longer propagation channels, it is important to characterize the vertical and horizontal distribution ...

Optical turbulence in the coastal area over False Bay /South Africa: Comparison of measurements and modeling results

The atmospheric influence on wave propagation was investigated during the First European South African Transmission ExpeRiment from June 2015 to February 2016. The focus in this article was set on optical turbulence, the main atmospheric factor affecting the position and strength of Laser beams, the performance of electro-optical systems and...

Investigation of the height dependency of optical turbulence in the surface layer over False Bay (South Africa)

Atmospheric turbulence impacts on the propagation of electro-optical radiation. Typical manifestations of optical turbulence are scintillation (intensity fluctuations), beam wander and (for laser systems) reduction of beam quality. For longer propagation channels, it is important to characterize the vertical and horizontal distribution ...

Comparison of integrated optical turbulence over the sea in different coastal regions in the world

Electro-optical and laser systems are presently deployed in naval operations around the world. The performance of these systems is negatively affected by optical turbulence in the atmosphere, quantified by the parameter Cn 2. The strength of the integrated optical turbulence Cn 2 was investigated for several coastal locations in different...

Atmospheric and laser propagation

This paper reviews three phenomena that affect the propagation of electro-optical radiation through the atmosphere: absorption and scattering, refraction and turbulence. The net effect on imaging or laser systems is a net reduction of the effective range, or a degradation of the information contained in the electro-optical radiation. Recent...

Long-term experiment VERTURM (vertical turbulence measurements): Comparison of measurements and modeling of the vertical distribution of optical turbulence Cn 2 in the surface layer

Operation and design of electro-optical systems are affected by atmospheric turbulence, quantified by refractive structure function parameter Cn 2. The long-term VerTurM experiment at a rural site in Northwestern Germany served to collect an extended dataset of vertical profiles of Cn 2 values up to 64 meters, completed by a characterization of...

First results on the Experiment FESTER on optical turbulence over False Bay South Africa: Dependencies and consequences

The experiment FESTER (First European South African Transmission ExpeRiment) took place in 2015 to investigate the atmospheric influence on electro-optical systems performance across False Bay / South Africa on a long term basis. Several permanent stations for monitoring electro-optical propagation and atmospheric parameters were set up around...

The dependence of optical turbulence on thermal and mechanical forces over the sea

Optical turbulence for over-water conditions was investigated in a long-term experiment over False Bay near Cape Town, South Africa. A sonic anemometer and two boundary-layer scintillometers were deployed to access in-situ turbulence as well as the integrated turbulence over two 1.8 and 8.7 km paths. Statistical analysis reveals spatial temporal...

Determination of atmospheric aerosol properties over land using satellite measurements

Mostly, aerosol properties are poorly understood because the aerosol properties are very sparse. The first workshop on the determination of atmospheric aerosol properties over land using satellite measurements is convened in Bremen, Germany. In this workshop, the topics of discussions included a variety of satellite aerosol optical thickness...

Point Target Extinction and Scintillation as function of range at LAPTEX, Crete

The range performance of IRST sensors is partly determined by the propagation of the atmosphere. For low altitude targets the boundary layer of the atmosphere introduces a variety of effects due to inhomogeneities, for which model predictions are not yet well validated. For this reason NATO Research Study Group 5 on "Maritime Infrared Target and...