The x-ray experiment on-board the “astron”

This paper describes the X-ray instrumentation, its capabilities and preliminary results which have been obtained for first two months operation.     

Ultrastructural and growth indices of Chlorella culture in multicomponent aquatic systems under space flight conditions.

Submicroscopic organization of Chlorella cells cultivated under space flight conditions in three-component aquatic system has been studied. Comparison of the experimental cells with that of the controls revealed certain rearrangements of cell organelles particularly, a reduction in the amount of reserve polysaccharides in chloroplasts, increase of cell vacuolization and mitochondrion volume, complication configuration of plasmalemma evaginations and invaginations, and also disturbances in the process of cytokinesis. More over an increase in the number of Chlorella cells infected by bacteria was shown in the experimental variant. No considerable differences were established in the growth characteristics of the experimental and control populations. A comparative cytological analysis revealed general regularities of organelles in Chlorella cells cultivated under space flight condition in the uni- and multicomponent systems.     

Whistler mode propagation in the earth and planetary magnetospheres and ray tracing techniques

Whistler mode wave phenomena observed in the earth's environment and in the planetary magnetospheres, such as in the vicinity of the Jupiter, Venus, and Saturn are reviewed, Importance of ray tracing technique is stated in connection with the interpretation of these phenomena. A historical review of ray tracing technique is then given. Finally the most recent ray tracing technique, such as 3-D ray tracing in a non-dipolar background magnetic field model is introduced.     

Adaptive Tracker Field-of-View Variation Via Multiple Model Filtering

Adaptive estimation using multiple model filtering is investigated as a means of changing the field of view as well as the bandwidth of an infrared image tracker when target acceleration can vary over a wide range. The multiple models are created by tuning filters for best performance at differing conditions of exhibited target behavior and differing physical size of their respective fields of view. Probabilistically weighted averaging provides the adaptation mechanism. Each filter involves online identification of the target shape function, so that this algorithm can be used against ill-defined and/or multiple-hot-spot targets. When each individual filter has the form of an enhanced correlator/linear Kalman filter, computational loading is very low. In contrast, an extended Kalman filter processing the raw infrared data directly and assuming a nonlinear constant turn-rate dynamics model provides superior tracking capability, especially for harsh maneuvers, at the cost of a larger computational burden.     

Pseudotransfer Function to Characterize a Hard Limiter

Results are reported on the attempt to define a pseudotransfer funtion of a circuit composed of a 2-pulse canceler and hard limiter.     

The Effect of Jamming on Monopulse Accuracy

An expression is applied for the probability density function (pdf) of the monopulse ratio when skin echoes from a passive target are contaminated by interference from a jammer. The analysis is valid for arbitrary signal-to-jam ratio and arbitrary locations of the target and jammer in the beam. For an on-axis skin target and a stand-off jammer at an off-axis location, the "pulling" effect of the jammer and the accuracy of the angle estimate are compared with the approximations currently employed in radar performance analysis. The pdf of the monopulse ratio for large and for small signal-to-jam ratios is presented, showing that the pdf is bimodal at small signal-to-jam ratio.     

Prediction of Adaptive Array Performance

A direct relationship between the conventional properties of an array and the array performance in an adaptive mode is given. Expressions are provided to obtain the output signal-to-interference-plus-noise ratio (SINR) of an adaptive array in terms of its conventinal pattern and the locations of the desired signal and jammers. These expressions permit one to evaluate the performance of an adaptive array without an exhaustive search for all possible scenarios and parametric values to ascertain that the required performance levels be met. In fact, one can predict the jammer locations for which the array will provide its best and worst performance by observing the conventional pattern. Several examples are provided to demonstrate the relationship between the conventional pattern and the adaptive array performance. The examples include both linear and planar arrays.     

Computational modeling of interference between helicopter main and tail rotors based on nonlinear blade vortex model

The Mi-2 helicopter was taken as an example for modeling the main and tail rotors operation with account for the interference at low speed sliding flight. Aerodynamic characteristics were calculated. The form of nonlinear vortical wake was obtained.