Dynamic Programming Solution for Detecting Dim Moving Targets

An on-board scanning or mosaic sensor is staring down from a satellite to a fixed ground point while producing a set of frames that contain target and background signals. Detecting dim moving targets should ideally be done by exhaustively searching over all in he maery(mached fltering), as ppoed possible trajectories in the imagery (matched filtering) as opposed to assembling trajectories from thresholded frames. The dynamic programming approach equivalently substitutes the above prohibitive exhaustive search by a feasible algorithm.     

The state of the art in D-region IRI modelling

While describing the formulation of IRI-79, in so far as it is applicable to the sub E-peak electron density profile, an attempt is made to compare its predictions with the available experimental evidence. The improvements needed for D-region electron density modelling are summarized. The current D-region IRI modelling effort is illustrated with a typical example.     

Mass loading of planetary magnetospheres by rocky satellites—I: Production of rocky ejecta

Recent hypervelocity studies have been conducted which simulate the collision of interplanetary dust with rocky planetary satellite surfaces. Preliminary flux-mass distributions of micron and submicron ejecta from these hypervelocity impact studies have been determined. Several models of the flux-mass distribution of primary interplanetary dust are used to determine ratios of satellite surface ejecta and primary meteoroid flux-mass distributions. The results are used in a second model to determine the ejecta spatial mass densities near the surface of the satellite.     

Observations of extragalactic objects with telescope ART-P onboard Granat

During 1990–1991 more than two dozens of extragalactic objects were observed by X-ray instruments aboard the Granat satellite. Among them there were AGNs and Seyfert galaxies (NGC4151, NGC5548, MCG-30-15, IC4329 etc.), quasars (3C273, 3C390.3 etc.), radio galaxies (Cen A, M87 etc.) and clusters of galaxies (Virgo, Perseus, Coma etc.). We will discuss below the preliminary results obtained with the ART-P telescope during the observations of five sources: NGC4151, 3C273, Cen A and the galaxies M87 and NGC4388 on the Virgo cluster.     

Bipolar-FET Combinational Power Transistors for Power Conversion Applications

Four bipolar-FET (field-effect transistor) combinational transistor configurations are compared from the application point of view. The configurations included are FET-Darlington (cascade), emitter-open switch (cascode), parallel configuration, and FET-gated bipolar transistors (FGT).     

Electron beam experiments in Japanese satellites and rockets

Electron beam experiments in space that have been done and planned in Japan are reviewed. 200eV, 1mA electron beam is emitted from a satellite and several types of wave excitation such as UHF and ω_ce have been observed. The satellite potential and the energy spectrum of returning electrons are measured by Langmuir probes and electrostatic energy analyser. In rocket experiments of K-10-11, K-10-12, K-9M-57, K-9M-58, K-9M-61 and K-9M-66, several types of electron guns were used whose power ranges from 1mW to 1KW. The rocket potential was measured by Langmuir probes and floating probes and optical line emission measurement and wave measurements were also done. The rocket potential was not so high as expected from the balance with ionospheric plasma but strongly affected by the plasma production by the emitted electron beam and return electrons.     

Fluid electrolyte and hormonal changes in conditioned and unconditioned men under hypokinesia

It has been suggested that hypokinesia (diminished muscular activity) may induce more changes in fluid electrolyte metabolism and hormonal concentration of blood plasma in conditioned than unconditioned men. Thus, the objective of this investigation was to determine the effect of 7 days of hypokinesis (HK) on fluid-electrolyte excretion and hormonal content of blood in 12 physically healthy men aged 19-23 years. They were divided into two equal groups according to their physical conditioning. For the simulation of the hypokinetic effect the men were kept under a rigorous bed rest regime. During the background period (BGP), that is prior to the exposure to HK, and under HK, the rate of elimination of fluid, sodium and potassium, and the content of blood plasma aldosterone and cortisol was measured. The amount of excretion of fluid and electrolytes increased while blood plasma aldosterone content decreased. In the conditioned men, a greater excretion of fluid and electrolytes and a greater reduction of plasma aldosterone concentration was observed. It was concluded that hypokinesia induced substantial changes in fluid-electrolyte excretion and hormonal content of blood plasma in both conditioned and unconditioned men.     

Blended control, predictor-corrector guidance algorithm: an enabling technology for Mars aerocapture

A guidance scheme designed for coping with significant dispersion in the vehicle's state and atmospheric conditions is presented. In order to expand the flyable aerocapture envelope, control of the vehicle is realized through bank angle and angle-of-attack modulation. Thus, blended control of the vehicle is achieved, where the lateral and vertical motions of the vehicle are decoupled. The overall implementation approach is described, together with the guidance algorithm macrologic and structure. Results of guidance algorithm tests in the presence of various single and multiple off-nominal conditions are presented and discussed.