Sensor validation using hardware-based on-line learning neuralnetworks

The objective of this document Is to show the capabilities of parallel hardware-based on-line learning neural networks (NNs). This specific application is related to an on-line estimation problem for sensor validation purposes. Neural-network-based microprocessors are starting to be commercially available. However, most of them feature a learning performed with the classic back-propagation algorithm (BPA). To overcome this lack of flexibility a customized motherboard with transputers was implemented for this investigation, The extended BPA (EBPA), a modified and more effective BPA, was used for the on-line learning, These parallel hardware-based neural architectures were used to implement a sensor failure detection, identification, and accommodation scheme in the model of a night control system assumed to be without physical redundancy in the sensory capabilities. The results of this study demonstrate the potential for these neural schemes for implementation in actual flight control systems of modern high performance aircraft, taking advantage of the characteristics of the extended back-propagation along with the parallel computation capabilities of NN customized hardware     

Gravisensitivity of cress roots.

The minimum dose (stimulus x time [gs]) eliciting a visible gravitropic response, has been determined using continuous and intermittent stimulation and two different accelerations at 1 g and 0.l g. The minimum dose of 20-30 gs estimated for microgravity roots and of 50-60 gs for roots grown on a 1 g-centrifuge indicated a higher sensitivity of microgravity roots. Applying intermittent stimuli to microgravity-grown roots, gravitropic responses were observed after two stimuli of 13.5 gs separated by a stimulus free interval of 118 s. The curvature of microgravity-grown roots to lateral stimulation by 0.1 g was remarkably smaller than by 1g in spite of the same doses which were applied to the seedlings. Microscopic investigations corresponding to stimulations in the range of the threshold values, demonstrated small displacement (< 2 micrometers) of statoliths in root statocytes. Accepting the statolith theory, one can conclude that stimulus transformation has to occur in the cytoplasm in close vicinity to the statoliths and that this transformation system was affected during seedling cultivation in microgravity.     

The atmospheric cosmic- and solar energetic particle radiation environment at aircraft altitudes

Galactic cosmic rays interact with the solar wind, the earth's magnetic field and its atmosphere to produce hadron, lepton and photon fields at aircraft altitudes. In addition to cosmic rays, energetic particles generated by solar activity bombard the earth from time to time. These particles, while less energetic than cosmic rays, also produce radiation fields at aircraft altitudes which have qualitatively the same properties as atmospheric cosmic rays. We have used a code based on transport theory to calculate atmospheric cosmic-ray quantities and compared them with experimental data. Agreement with these data is seen to be good. We have then used this code to calculate equivalent doses to aircraft crews. We have also used the code to calculate radiation doses from several large solar energetic particle events which took place in 1989, including the very large event that occurred on September 29^th and 30^th of that year. The spectra incident on the atmosphere were determined assuming diffusive shock theory.     

Determination of the threshold acceleration for the gravitropic stimulation of cress roots and hypocotyls.

To determine the range of the threshold acceleration (a-threshold) for the gravitropic stimulation of Lepidium sativum L. roots and hypocotyls, experiments were performed on a centrifuge-clinostat with two-orthogonal axes. The rotation rate of the clinostat was 4 rpm (< or = 1.8 x 10(-4) g), while that of the centrifuge was from 3 to 17 rpm (3 x 10(-3) to 10(-1) g). The gravitropic response was determined: (i) after growth of roots and hypocotyls in their normal vertical position and subsequent gravitropic stimulation for 3 h by accelerations of 4 x 10(-3) to 10(-1) g, and (ii) after continuous stimulation in the lateral direction by centripetal accelerations of 4 x 10(-3) to 10(-1) g. The a-threshold was defined by an extrapolation of the regression line of R = p + rx, where x was either ln a or l/a for 3 h or a continuous stimulation, respectively. The a-threshold estimated after 3 h stimulation was equal to 2.6 x 10(-3) g for roots and 3.1 x 10(-3) g for hypocotyls. The threshold accelerations that were unable to evoke a gravitropic response even with continuous stimulation of cress roots and hypocotyls were approximately 3.1 x 10(-3) g and 3.6 x 10(-3) g, respectively. Increasing the stimulation acceleration up to 4.1 x 10(-3) g led to a statistically confirmed gravitropic response of a definite proportion of both the root and hypocotyl populations. In the experiments where acceleration and stimulation time were variable, the threshold dose (D-threshold) for roots was determined to be about 14 to 22 g x s, depending on the stimulation duration and the range of accelerations. The kinetics of gravitropic response at a near-threshold acceleration (4 x 10(-3) to 1.9 x 10(-2) g) differed from that at 1 g (horizontal stimulation). At low forces, the maximal response dependent on the magnitude of acceleration could not be enhanced by increasing the stimulation time up to at least 210 min.     

Low altitude dose measurements from APEX, CRRES and DMSP

Dosimeter data taken on the APEX (1994–1996), CRRES (1990–1991) and DMSP (1984–1987) satellites have been used to study the low altitude (down to 350 km) radiation environment. Of special concern has been the inner edge of the inner radiation belt due to its steep gradient. We have constructed dose models of the inner edge of the belt from all three spacecraft and put them into a personal computer utility, called APEXRAD, that calculates dose for user-selected orbits. The variation of dose for low altitude, circular orbits is given as a function of altitude, inclination and particle type. Dose-depth curves show that shielding greater than 1/4 in Al is largely ineffectual for low altitude orbits. The contribution of outer zone electrons to low altitude dose is shown to be important only for thin shields and to have significant variation with magnetic activity and solar cycle.     

Special features of a digital speckle interferometer for determining vibration characteristics of heavy-loaded elements of an aircraft fuel pump

The results of vibration tests for heavy-loaded elements in the auger-centrifugal stage of an aircraft fuel pump performed with the use of an interference-free digital speckle-interferometer created at the Samara State Aerospace University are presented. The speckle-interferograms of an auger and a centrifugal wheel of the auger-centrifugal pump stage in different conditions of attachment and dynamic loading are given. The data obtained may be of sufficient importance in the development of aircraft fuel pumps for a specified service life.     

Optimization of efficient order service by information unmanned aerial vehicles

We propose a mathematical model and the numerical method for an optimal choice of unmanned aerial vehicles (UAVs) from those being in flight to fulfill a newly received order for monitoring (reconnaissance) of a new region. Examples of using the approach being proposed and main lines of its realization in promising information unmanned aircraft complexes (UAC) are presented.     

Effects of a “day-time” substorm on the ionosphere and radio propagation

Propagation mechanisms of lateral (non-great-circle) signals on a high-latitude HF radio path during magnetospheric substorms that occurred in the day-time have been considered. The path is equipped with oblique ionospheric sounding (OIS) from Murmansk to St. Petersburg. The OIS method gives the possibility to determine propagation modes, MOF (maximum observed frequency) values, signal delays, etc. Data of the CUTLASS radar, the IMAGE magnetometer system, the Finnish riometer chain, and the Tromso ionosonde were also used for the analysis. The main results are the following: (1) the lateral signal propagation takes place, as a rule, if the path midpoint is located near the irregularity region that moves sharply from high to low latitudes. The lateral signal propagation appearing during day-time is a new effect. (2) Formation of dense field-aligned irregularities during a substorm leads to decreasing F2MOF values on radio paths. These results can be useful for problems of radiolocation, HF communications and navigation.     

Comparative study of productivity of the Rosetta target Comet 67P/Churyumov-Gerasimenko

In an attempt to evaluate correlations between several properties of comets we report the results of a cometary research involving a criterious analysis of gas and dust mass production rates in Comets 67P/Churyumov-Gerasimenko (main target of Rosetta Mission), 1P/Halley, Hyakutake (C/1996 B2), and 46P/Wirtanen and make a comparison between them.     

General dynamics in the Restricted Full Three Body Problem

The problem of a binary system and a spacecraft in its gravity field is studied. As the mass distribution of the bodies is considered, the two problems are referred as the Full Two Body Problem (F2BP) and the Restricted Full Three Body Problem (RF3BP), respectively. The conditions for relative equilibria and their stability in the F2BP were derived for an ellipsoid–sphere system. As the non-equilibrium problem is more common in nature, we look at periodic orbits in the F2BP close to the relative equilibrium conditions. It is found that families of periodic orbits can be computed where the minimum energy state of one family is the relative equilibrium state. An approximation method was derived in order to facilitate the computation of periodic orbits near relative equilibria while keeping the interesting dynamical features. The next step is to make the connection between the dynamics of the RF3BP and the F2BP. In the current paper, we solve for the dynamics of the F2BP and substitute this model in the RF3BP. We provide a basic investigation of the dynamics of a particle in the gravitational field of this binary system. We show results in the F2BP and the RF3BP.