Main characteristics of biological components of developing life support system observed during the experiments aboard orbital complex MIR.

Since 1990, the orbital complex MIR has witnessed several incubator experiments for determination of spaceflight effects on embryogenesis of Japanese quail. First viable chicks who had completed the whole embryological cycle in MIR microgravity hatched out in 1990; it became clear that newborns would not be able to adapt to microgravity unaided. There were 8 successful incubations of chicks in the period from 1990 to 1999. In 1995-1997 the MIR-NASA space science program united Russian and US investigators. As a result, experiments Greenhouse-1 and 2 were performed with an effort to grow super dwarf wheat from seed to seed, and experiment Greenhouse-3 aimed at receiving two successive generations of Brassica rapa. But results of these experiments could not be used for definitive conclusions concerning effects of spaceflight on plant ontogenesis and, therefore, experiments Greenhouse-4 and 5 were staged within the framework of the Russian national space program. The experiments finally yielded wheat seeds. Some of the seeds was left on the space station and, being planted, gave viable seedlings which, in their turn, produced the second crop of space seeds.     

Novel array-feed distortion compensation techniques for reflectorantennas

Degradation of antenna performance by reflector surface distortion, which lowers gain and increases sidelobe levels, is addressed. Distortion compensation concepts based on the applications of properly matched array feeds are presented. Results of conceptual developments, numerical simulations, and measurement verifications are presented in support of this approach, with particular attention to the measurement technique. It is shown that the concept is most useful for overcoming the deterioration effects of slowly varying surface distortions, which would make the method very useful for future large space and ground antennas. It is further shown that for a typical, slowly varying thermal or gravitational surface distortion, a 19-element array feed can improve the reflector performance considerably     

Sequential Scene Matching Using Edge Features

When radar and optical images are examined in detail, it is often found that the most distinguishable common feature of the two types of images is the shapes of various natural as well as man-made objects. An edge-extraction technique was developed and used to extract the salient edges of the objects of interest. A sequential, hierarchical search technique was implemented in the matching of the images using the edge features.     

D-region IRI profiles in relation to radio observations

The D-region IRI profiles are compared with the direct rocket measurements as well as with ground-based radio observations by a variety of techniques. The characteristics of D-region IRI profiles and the dependence of electron density on solar zenith angle, sunspot number, latitude and season are discussed. The sensitivity of certain reflection coefficients on the height distribution of electron density below 70 km is illustrated with a typical example. For D-region modelling, the results show the importance of simultaneous measurement of reflection and conversion coefficients together with polarization phase over a wide frequency range.     

Nonlinear Analysis of a Family of LC Tuned Inverters

four widely used self-oscillating dc-to-square-wave parallel inverters which employ an inductor-capacitor tuned network to determine the oscillation frequency are reduced to a common equivalent RLC network. The techniques of singular-point analysis and state-plane interpretations are employed to describe the steady-state and transient ient behavior of these circuits and to elucidate the three possible modes of operation: quasi-harmonic, relaxation, and discontinuous. Design guidelines are provided through a study of the influence of circuit parameter variations on the characteristics of oscillation and on frequency stability. Several examples are provided to illustrate the usefulness of this analysis when studying such problems as transistor emitter-to-base junction breakdown during oscillations and the design of starting circuits to insure self-excited oscillations in these inverters.     

Effects of air velocity on photosynthesis of plant canopies under elevated CO2 levels in a plant culture system.

To obtain basic data for adequate air circulation for promoting plant growth in closed plant production modules in bioregenerative life support systems in space, effects of air velocities ranging from 0.1 to 0.8 m s-1 on photosynthesis in tomato seedlings canopies were investigated under atmospheric CO2 concentrations of 0.4 and 0.8 mmol mol-1. The canopy of tomato seedlings on a plug tray (0.4 x 0.4 m2) was set in a wind-tunnel-type chamber (0.6 x 0.4 x 0.3 m3) installed in a semi-closed-type assimilation chamber (0.9 x 0.5 x 0.4 m3). The net photosynthetic rate in the plant canopy was determined with the differences in CO2 concentrations between the inlet and outlet of the assimilation chamber multiplied by the volumetric air exchange rate of the chamber. Photosynthetic photon flux (PPF) on the plant canopy was kept at 0.25 mmol m-2 s-1, air temperature at 23 degrees C and relative humidity at 55%. The leaf area indices (LAIs) of the plant canopies were 0.6-2.5 and plant heights were 0.05-0.2 m. The net photosynthetic rate of the plant canopy increased with increasing air velocities inside plant canopies and saturated at 0.2 m s-1. The net photosynthetic rate at the air velocity of 0.4 m s-1 was 1.3 times that at 0.1 m s-1 under CO2 concentrations of 0.4 and 0.8 mmol mol-1. The net photosynthetic rate under CO2 concentrations of 0.8 mmol mol-1 was 1.2 times that under 0.4 mmol mol-1 at the air velocity ranging from 0.1 to 0.8 m s-1. The results confirmed the importance of controlling air movement for enhancing the canopy photosynthesis under an elevated CO2 level as well as under a normal CO2 level in the closed plant production modules.     

Direct observation of charge state abundances of energetic He,C, O,and Fe emitted in solar flares

The ionic charge states of helium, carbon, oxygen, and iron have been determined for three solar particle enhancements by an electrostatic deflection analyzer, which is combined with a thin window proportional counter dE/dX vs. E system. The observations are obtained during the periods September 23 to 29, 1978, June 6 to 8, 1979, and September 15 to 26, 1979, with an instrument onboard the ISEE-3 spacecraft. The mean ionic charge states for He, C, and oxygen exhibit a high degree of ionization with values of Q = 2, 6, and 7.2, respectively. The charge state of iron is near 13 charge units. Variations from flare to flare and within the September 23, 1978 flare are small. The most surprising feature of the charge state measurement is the observation of a small (～10%) but finite contribution of singly ionized helium.     

The Application of Digital Techniques to a VOR Signal Generator

The design of a high-accuracy digital VOR signal generator is described. The main part of the generator is formed of three digital sinewave generators, one of which is frequency modulated. The equations needed to design these generators are given and the practical realization based on read-only memories is described.     

Performance Evaluation of Energy Detectors

The prediction of energy detector performance requires a complicated calculation or a tedious manipulation of nomograms. For a large time-bandwidth product WT, however, it is commonplace to use the formula (E/No) = d?WT to anticipate the required average input energy-to-noise spectral density ratio for a wanted signal detectability parameter d and thus avoid the computational difficulty. This paper proposes a modified formula (E/No) = ?d?WT that is applicable for all range of WT, where ? is the modification factor derived on an empirical basis. The Van Trees measure of the signal detectability parameter of the energy detector also is derived analytically and compared to the modified equation.