KEYWORDS: Sensors, Databases, Monte Carlo methods, Error analysis, Calibration, Missiles, Statistical analysis, Sensor performance, Signal to noise ratio, Data modeling
The development of a discrimination software testbed, the Discrimination Requirements Model (DRM), intended to support IR sensor requirements definition is described. The DRM employs the standard pattern recognition paradigm, e.g., the reduction of a Monte Carlo database of noised input object signatures into the corresponding target and non-target feature vector sets. Classification of the feature vectors is performed using a varied threshold. The false alarm (PFA) and leakage (PL) error probabilities are estimated via a leave-one- out procedure. The resultant PFA versus PL curve of user selectable thresholds is used to evaluate discrimination performance for the test signature database. Degradation of input signature data strings is accomplished through a set of user selectable sensor performance capabilities. The selectable feature subset includes statistical, curvilinear fit, dynamical, and centralized moment-based parameters for single and multiple band optical systems as well as various normalization options. The DRM accommodates dropouts and other realistic SNR effects. A centralized approach is employed for multiple sensor data fusion for discrimination based on prior associated object tracks. Applications to sensor design and system performance projections are discussed.
We describe the development of a 3-D statistically nonstationary earthlimb stochastic structure representation and its application to earthlimb infrared (IR) background structure simulations. An earthlimb viewing geometry is defined by the location of both observer and source in space. The line-of-sight tangent altitude is the minimum altitude of the trajectory, defined at the earth-centered perpendicular to the line of sight. The stochastic structure overlay is constructed from a 2-D diagonal cut through a 3-D matrix of correlated Gaussian deviates; each plane of the matrix represents a statistically constant representation of the 2-D correlation lengths at a given altitude above the earth. Each matrix plane is generated using successive 2-D fast Fourier transform routines that have empirical values of vertical and horizontal correlation lengths as input. The total deviate variance versus altitude is then scaled from empirical measurements of fluctuations in atmospheric density, temperature, and/or emissivity. These structure generators are used both as perturbations on input atmospheric data to IR radiance codes and as high-resolution overlays to earthlimb lR mean-radiance 2-D scenes. An IR structured scene realization and scene validation analysis is presented.
This paper describes the development of a 3-D statistically non-stationary earthlimb stochastic structure representation and its application to the implementation of earthlimb infrared (IR) structured scenes. The stochastic structure overlay is constructed from a 2-D diagonal cut through a 3-D matrix of correlated Gaussian deviates: each plane of the matrix represents a statistically constant representation of the two-dimensional correlation lengths at a given altitude above the earth. Each matrix plane is generated by using successive 2-D FFT routines that have empirical values of vertical and horizontal correlation lengths as input. The total deviate variance versus altitude is then scaled from empirical measurements of fluctuations in atmospheric density, temperature, and/or emissivity. Scene correlation lengths are validated by performing diagnostics on the overlays. These structures generators have been used both as perturbations on input atmospheric data to earthlimb IR radiance codes and as high resolution overlays to earthlimb IR mean radiance 2-D scenes. Examples of modeling results are presented and discussed.
The standard FFT, optical propagation computer code-applicable method for calculating realizations of phase screens to simulate the effects of atmospheric turbulence is presently modified to include such LF aberrations as tilt. It is shown that the modified phase screens yield superior statistical representations of Kolmogorov turbulence, and comparisons of simulations employing such modified phase screens with the results of theoretical calculations for Strehl ratio with finite outer-scale effects are presented. The modified method is noted to be highly memory-efficient, relative to the phase screens used for the propagation simulations.
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