BIOS-4 as an embodiment of CELSS development conception.

Any attempt to create LSS for practical applications must take into account the possibility of castastrophic consequences if the problem of LSS reliability and stability is not solved. An integrated conception of CELSS studies development as a possible way to increase its reliability is considered. The BIOS-4 facility project is developed in the context of the conception. Three principles of highly effective experimental CELSS facility design are proposed. Some details of BIOS-4 design and its exploitation features are presented.     

Simulation experiments of the effect of space environment on bacteriophage and DNA thin films.

The main goal of PUR experiment (phage and uracil response) is to examine and quantify the effect of specific space conditions on nucleic acid models. To achieve this an improved method was elaborated for the preparation of DNA and bacteriophage thin films. The homogeneity of the films was controlled by UV spectroscopy and microscopy. To provide experimental evidence for the hypothesis that interplanetary transfer of the genetic material is possible, phage T7 and isolated T7 DNA thin films have been exposed to selected space conditions: intense UVC radiation (lambda=254 nm) and high vacuum (10(-4) Pa). The effects of DNA hydration, conformation and packing on UV radiation damage were examined. Characteristic changes in the absorption spectrum, in the electrophoretic pattern of DNA and the decrease of the amount of PCR products have been detected indicating the photodamage of isolated and intraphage DNA.     

Sequence comparison techniques for multisensor data fusion andtarget recognition

A new class of techniques for multisensor fusion and target recognition is proposed using sequence comparison by dynamic programming and multiple model estimation. The objective is to fuse information on the kinematic state and “nonkinematic” signature of unclassified targets, assessing the joint likelihood of all observed events for recognition. Relationships are shown to previous efforts in pattern recognition and state estimation. This research applies “classical” speech processing-related and other sequence comparison methods to moving target recognition, extends the efforts of previous researchers through improved fusion with kinematic information, relates the proposed techniques to Bayesian theory, and applies parameter identification methods to target recognition for improved understanding of the subject in general. The proposed techniques are evaluated and compared with existing approaches using the method of generalized ambiguity functions, which lends to a form of Cramer-Rao lower bound for target recognition     

AFIT neural network research

A brief summary of research done at the Air Force Institute of Technology (AFIT) in the area of neural networks is provided. It has been shown that backpropagation, used for feedforward artificial neural networks, is just a degenerate version of an extended Kalman filter, and that networks can do about as well as the optimum statistical classification technique. A method of finding the importance of features for use by a neural network classifier has been determined. Techniques for using neural networks for image segmentation have been developed. In optical pattern recognition, techniques that allow the processing of real FLIR (forward-looking infrared) images with existing binary spatial light modulators have been devised. An optical direction of arrival detector applicable to laser illumination direction determination has been designed and tested; the design is similar to a fly's eye. Coated mirrors for the optical confocal Fabry-Perot interferometer have been designed, specified, fabricated, and installed. Significant progress has been made in the use of neural networks for processing multiple-feature sets for speech recognition     

Practical stabilization in attitude thruster control

The attitude stabilization of a spacecraft using thrusters is considered from a practical point of view, i.e., when actuator constraints, uncertainties and failures, measurement noise, fuel consumption, and inertia matrix uncertainty are considered. A variable structure controller based on sliding modes is obtained first, which guarantees global exponential stability under actuator constraints, uncertainties, and failures. The design is based on a continuous average-proportional torque selection function and a set of feasible sliding surfaces, which may be adapted to improve performance. Exponential convergence towards ultimate bounds is guaranteed when all other practical issues arise.     

A wavelet multiresolution analysis for spatio-temporal signals

The wavelet filters of the conventional 3D multiresolution analysis possess homogeneous spatial and temporal frequency characteristics which limits one's ability to match filter frequency characteristics to signal frequency behavior. Also, the conventional 3D multiresolution analysis employs an oct-tree decomposition structure which restricts the analysis of signal details to identical resolutions in space and time. This paper presents a 3D wavelet multiresolution analysis constructed from nonhomogeneous spatial and temporal filters, and an orthogonal sub-band coding scheme that decouples the spatial and temporal decomposition processes     

How much of the solar irradiance variations is caused by the magnetic field at the solar surface?

The contribution to total solar irradiance variations by the magnetic field at the solar surface is estimated. Detailed models of the irradiance changes on the basis of magnetograms show that magnetic features at the solar surface account for over 90% of the irradiance variations on a solar rotation time scale and at least 70% on a solar cycle time scale. If the correction to the VIRGO record proposed by Fröhlich & Finsterle (2001) is accepted, then magnetic features at the solar surface are responsible for over 90% of the solar cycle irradiance variations as well.     

Design and implementation of near-field, wideband synthetic aperture beamformers

A coarray-based near-field, wideband synthetic aperture beamformer using stepped-frequency signal synthesis and post-data acquisition processing is presented. While coarray techniques offer significant reduction in the number of array elements for a given angular resolution, the hybrid subarray-stepped frequency realization of wideband systems simplifies implementations and offers flexibility in beamforming. Proof of concept is provided using real data collected in an anechoic chamber for several pulse shapes and array weightings.     

Parametric Rao Test for Multichannel Adaptive Signal Detection

The parametric Rao test for a multichannel adaptive signal detection problem is derived by modeling the disturbance signal as a multichannel autoregressive (AR) process. Interestingly, the parametric Rao test takes a form identical to that of the recently introduced parametric adaptive matched filter (PAMF) detector for space-time adaptive processing (STAP) in airborne surveillance radar systems and other similar applications. The equivalence offers new insights into the performance and implementation of the PAMF detector. Specifically, the Rao/PAMF detector is asymptotically (for large samples) a parametric generalized likelihood ratio test (GLRT), due to an asymptotic equivalence between the Rao test and the GLRT. The asymptotic distribution of the Rao test statistic is obtained in closed form, which follows an exponential distribution under the null hypothesis H ₀ and, respectively, a noncentral Chi-squared distribution with two degrees of freedom under the alternative hypothesis H ₁. The noncentrality parameter of the noncentral Chi-squared distribution is determined by the output signal-to-interference-plus-noise ratio (SINR) of a temporal whitening filter. Since the asymptotic distribution under H ₀ is independent of the unknown parameters, the Rao/PAMF asymptotically achieves constant false alarm rate (CFAR). Numerical results show that these results are accurate in predicting the performance of the parametric Rao/PAMF detector even with moderate data support.