Optics in Atmospheric Propagation and Adaptive Systems XIII, 2010
The FATMOSE trial (FAlse-bay ATMOSpheric Experiment) running over a period from November 2009 to ... more The FATMOSE trial (FAlse-bay ATMOSpheric Experiment) running over a period from November 2009 to July 2010, was a continuation of the cooperation between TNO and IMT on atmospheric propagation and point target detection and identification in a maritime environment. Instruments were installed for measuring scintillation, blurring- and refraction effects over a 15.7 km path over sea. Simultaneously, a set of
Optics in Atmospheric Propagation and Adaptive Systems XIV, 2011
Knowledge on the marine boundary layer is of importance for the prediction of the optical image q... more Knowledge on the marine boundary layer is of importance for the prediction of the optical image quality obtained from long range targets. One property of the boundary layer, that can be studied rather easily by means of optical refraction measurements, is the vertical temperature profile. This profile can be compared with the profile, as predicted by the generally accepted Monin-Obukhov
Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XX, 2009
ABSTRACT During the False Bay trial (June 2007), the performance of a set of three optical sensor... more ABSTRACT During the False Bay trial (June 2007), the performance of a set of three optical sensors was tested against several small surface targets in a coastal area: a hyperspectral camera, a camera with a rotating polarization filter and a high resolution camera. One objective was the validation of a contrast and clutter model for the visual spectral band in this type of scenarios. Another issue was to test the benefit of using a polarisation filter and a hyperspectral unit in front of standard TV cameras. Finally the loss in identification capability of a high resolution camera at long range due to atmospheric blur was investigated. Data were collected of targets in near-sun direction at ranges up to seven kilometers, in all cases for down looking angles (targets below the horizon). Environmental parameters such as solar irradiance and windspeed were measured as input for the contrast and clutter models. Spatial, spectral and temporal effects of the target contrast and of the background clutter behaviour in the visual spectral band were determined as function of range and compared with model predictions. Samples of data and predictions are presented in this paper. The spatial and temporal target characteristics are of key importance for the development of algorithms for target detection, classification and tracking. Finally, rules of thumb, based on the measurements and model predictions, on the detection and identification range performances of specific optical sensors against small surface targets in a maritime environment are presented.
Atmospheric Optics IV: Turbulence and Propagation, 2011
The FATMOSE trial (False Bay Atmospheric Experiment) is a continuation of the cooperative work be... more The FATMOSE trial (False Bay Atmospheric Experiment) is a continuation of the cooperative work between TNO and IMT on atmospheric propagation and point target detection and identification in a maritime environment (South Africa). The atmospheric transmission, being of major importance for target detection, was measured with the MSRT multiband optical/IR transmissometer over a path of 15.7 km over sea. Simultaneously
Optics in Atmospheric Propagation and Adaptive Systems XV, 2012
ABSTRACT The knowledge on scintillation, caused by atmospheric turbulence, is of vital importance... more ABSTRACT The knowledge on scintillation, caused by atmospheric turbulence, is of vital importance for the performance prediction of threat detection systems and for the development of associated detection algorithms. Additionally, scintillation data may support the knowledge on turbulence characteristics. Along these ideas, data have been analysed, collected during the FATMOSE trials, carried out over the False Bay (South Africa) over a range of 15.7 km from November 2009 until October 2010. The collected data include long-range scintillation measurements, taken with the MSRT radiometer and a modulated source and with a high resolution imager and static sources. In addition a standard scintillometer was used over a short range, 1.8 km parallel path and a mid-path sonic anemometer for direct measurement of windspeed and air temperature fluctuations. Indirectly, information on turbulence parameters is predicted from the weather data, collected at the mid-path station, by using our TARMOS code for the marine boundary layer. Details on the set-up and the method of analysis are given, including some relevant examples. Scintillation spectra between 0.1 and 100 Hz are shown for investigation of the validity of Kolmogorov's theory of turbulence. In addition, signal (irradiance) statistics are shown for testing the log-normality of their characteristics. In relation to this, attention is spent on the subject of saturation of scintillation, which may occur in conditions of strong turbulence, combined with small apertures and long ranges. Output from the various sensors is compared with TARMOS predictions and related to the simultaneously collected blur and beam wander data. Related to this, data on the signal correlations from the various MSRT apertures provide information on the transverse atmospheric coherence length rho(0), which parameter is directly linked to the blur. Examples are shown of the wavelength dependence of scintillation, predicted from the theory of weak turbulence, in comparison with the 3-band scintillation data from the MSRT sensor. In the comparison of the local and path-averaged scintillation, the effect of path inhomogeneities of the atmospheric conditions along the path is taken into account. Conditions with low scintillation are getting special attention, as they do not always correspond to conditions with small blur.
Optics in Atmospheric Propagation and Adaptive Systems XIII, 2010
The FATMOSE trial (FAlse-bay ATMOSpheric Experiment) running over a period from November 2009 to ... more The FATMOSE trial (FAlse-bay ATMOSpheric Experiment) running over a period from November 2009 to July 2010, was a continuation of the cooperation between TNO and IMT on atmospheric propagation and point target detection and identification in a maritime environment. Instruments were installed for measuring scintillation, blurring- and refraction effects over a 15.7 km path over sea. Simultaneously, a set of
Optics in Atmospheric Propagation and Adaptive Systems XIV, 2011
Knowledge on the marine boundary layer is of importance for the prediction of the optical image q... more Knowledge on the marine boundary layer is of importance for the prediction of the optical image quality obtained from long range targets. One property of the boundary layer, that can be studied rather easily by means of optical refraction measurements, is the vertical temperature profile. This profile can be compared with the profile, as predicted by the generally accepted Monin-Obukhov
Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XX, 2009
ABSTRACT During the False Bay trial (June 2007), the performance of a set of three optical sensor... more ABSTRACT During the False Bay trial (June 2007), the performance of a set of three optical sensors was tested against several small surface targets in a coastal area: a hyperspectral camera, a camera with a rotating polarization filter and a high resolution camera. One objective was the validation of a contrast and clutter model for the visual spectral band in this type of scenarios. Another issue was to test the benefit of using a polarisation filter and a hyperspectral unit in front of standard TV cameras. Finally the loss in identification capability of a high resolution camera at long range due to atmospheric blur was investigated. Data were collected of targets in near-sun direction at ranges up to seven kilometers, in all cases for down looking angles (targets below the horizon). Environmental parameters such as solar irradiance and windspeed were measured as input for the contrast and clutter models. Spatial, spectral and temporal effects of the target contrast and of the background clutter behaviour in the visual spectral band were determined as function of range and compared with model predictions. Samples of data and predictions are presented in this paper. The spatial and temporal target characteristics are of key importance for the development of algorithms for target detection, classification and tracking. Finally, rules of thumb, based on the measurements and model predictions, on the detection and identification range performances of specific optical sensors against small surface targets in a maritime environment are presented.
Atmospheric Optics IV: Turbulence and Propagation, 2011
The FATMOSE trial (False Bay Atmospheric Experiment) is a continuation of the cooperative work be... more The FATMOSE trial (False Bay Atmospheric Experiment) is a continuation of the cooperative work between TNO and IMT on atmospheric propagation and point target detection and identification in a maritime environment (South Africa). The atmospheric transmission, being of major importance for target detection, was measured with the MSRT multiband optical/IR transmissometer over a path of 15.7 km over sea. Simultaneously
Optics in Atmospheric Propagation and Adaptive Systems XV, 2012
ABSTRACT The knowledge on scintillation, caused by atmospheric turbulence, is of vital importance... more ABSTRACT The knowledge on scintillation, caused by atmospheric turbulence, is of vital importance for the performance prediction of threat detection systems and for the development of associated detection algorithms. Additionally, scintillation data may support the knowledge on turbulence characteristics. Along these ideas, data have been analysed, collected during the FATMOSE trials, carried out over the False Bay (South Africa) over a range of 15.7 km from November 2009 until October 2010. The collected data include long-range scintillation measurements, taken with the MSRT radiometer and a modulated source and with a high resolution imager and static sources. In addition a standard scintillometer was used over a short range, 1.8 km parallel path and a mid-path sonic anemometer for direct measurement of windspeed and air temperature fluctuations. Indirectly, information on turbulence parameters is predicted from the weather data, collected at the mid-path station, by using our TARMOS code for the marine boundary layer. Details on the set-up and the method of analysis are given, including some relevant examples. Scintillation spectra between 0.1 and 100 Hz are shown for investigation of the validity of Kolmogorov's theory of turbulence. In addition, signal (irradiance) statistics are shown for testing the log-normality of their characteristics. In relation to this, attention is spent on the subject of saturation of scintillation, which may occur in conditions of strong turbulence, combined with small apertures and long ranges. Output from the various sensors is compared with TARMOS predictions and related to the simultaneously collected blur and beam wander data. Related to this, data on the signal correlations from the various MSRT apertures provide information on the transverse atmospheric coherence length rho(0), which parameter is directly linked to the blur. Examples are shown of the wavelength dependence of scintillation, predicted from the theory of weak turbulence, in comparison with the 3-band scintillation data from the MSRT sensor. In the comparison of the local and path-averaged scintillation, the effect of path inhomogeneities of the atmospheric conditions along the path is taken into account. Conditions with low scintillation are getting special attention, as they do not always correspond to conditions with small blur.
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