Stochastic game approach to air operations

A command and control (C/sup 2/) problem for military air operations is addressed. Specifically, we consider C/sup 2/ problems for air vehicles against ground-based targets and defensive systems. The problem is viewed as a stochastic game. We restrict our attention to the C/sup 2/ level where the problem may consist of a few unmanned combat air vehicles (UCAVs) or aircraft (or possibly teams of vehicles), less than say, a half-dozen enemy surface-to-air missile air defense units (SAMs), a few enemy assets (viewed as targets from our standpoint), and some enemy decoys (assumed to mimic SAM radar signatures). At this low level, some targets are mapped out and possible SAM sites that are unavoidably part of the situation are known. One may then employ a discrete stochastic game problem formulation to determine which of these SAMs should optimally be engaged (if any), and by what series of air vehicle operations. We provide analysis, numerical implementation, and simulation for full state-feedback and measurement feedback control within this C/sup 2/ context. Sensitivity to parameter uncertainty is discussed. Some insight into the structure of optimal and near-optimal strategies for C/sup 2/ is obtained. The analysis is extended to the case of observations which may be affected by adversarial inputs. A heuristic based on risk-sensitive control is applied, and it is found that this produces improved results over more standard approaches.     

On electromagnetic phenomena in Mercury’s magnetosphere

Mercury has a small but intriguing magnetosphere. In this brief review, we discuss some similarities and differences between Mercury’s and Earth’s magnetospheres. In particular, we discuss how electric and magnetic field measurements can be used as a diagnostic tool to improve our understanding of the dynamics of Mercury’s magnetosphere. These points are of interest to the upcoming ESA-JAXA BepiColombo mission to Mercury.     

Solar wind turbulence during the solar cycle deduced from Galileo coronal radio-sounding experiments

Seven coronal radio-sounding campaigns were carried out during the active lifetime of the Galileo spacecraft in the years 1994–2002. The observational data analyzed in the present work are S-band frequency fluctuation measurements recorded during the solar conjunctions at different phases of solar activity cycle #23, specifically: periods near solar maximum (three conjunctions), near solar minimum (three conjunctions) and during the ascending phase (one conjunction). These data are all applicable to low heliographic latitudes, i.e. to the slow solar wind. The rms frequency fluctuation and power-law index of the frequency fluctuation temporal spectra are determined as a function of heliocentric distance. The turbulence power spectrum tends to be flatter inside ca. 20 solar radii during all phases of the solar cycle. This coincides with a transition in the flow from the inner acceleration region to the outer region of constant velocity. The radial falloff rate and absolute level of the rms frequency fluctuation are essentially invariant over the solar cycle.     

Integral-projection method and singularities of its application in mating shells with inconsistent parameters of approximation

We describe a numerical integral-projection method used by the authors for the approximate solution of systems of interrelated two-dimensional linear boundary-value problems in mechanics of composite shell systems. The method is based on discretization in each shell substructure of a two-dimensional problem along one of coordinates using a projection-grid variant of the Galerkin-Petrov method and its subsequent transformation to a system of ordinary differential equations; by integration and introduction of sought functions as unknown derivatives, the system is reduced to a system of integral equations being solved by the method of mechanical quadratures. The method is characterized by the fact that its application requires no additional conditions of conformity with discretization parameters of substructures being mated.     

Progress in ultrasonic bioreactors for CELSS applications.

An important issue in Controlled Ecological Life Support Systems (CELSS) is the recycling of inedible crop residues to recover inorganic plant nutrients such as nitrates, phosphates, potassium and other macro- and micro-nutrients. In a closed system in space, such regeneration is vital to the long term viability of plant growth necessary for the food production and waste handling process. Chemical approaches to recycling such as incineration and wet oxidation are not compatible with low energy and environmentally friendly regeneration of such nutrients. Biological regeneration is more acceptable environmentally, but it is a very slow process and does not typically result in complete recovery of inorganic and organic nutrients. A new approach to biological regeneration is described here involving the combined use of special enzymatic catalysts and ultrasonic energy in a bioreactor system. This new system has the potential for rapid, efficient, environmentally friendly and complete conversion of crop wastes to inorganic plant nutrients and food recovery from cellulose materials. A series of experimental tests were carried out with a soybean crop residue meal substrate. Biochemical conversion rates were significantly expedited with the addition of enzymes and further enhanced through ultrasonic stimulation of these enzymes. The difference in conversion rates was particularly increased after the initial period of soluble organics conversion. The remaining cellulose substrate is much more difficult to biodegrade, and the ultrasonically-enhanced reaction was able to demonstrate a much higher rate of substrate conversion.     

Statistical method for ground and sky coverage calculation

A novel statistical method has been devised for evaluating the ground and the sky coverage of an observation experiment on board a satellite. Owing to its unrivalled rapidity compared with other conventional calculation techniques, the method can be applied to evaluate the coverage percentages for the whole globe or any area on it, to calculate the visibility percentages for one or more ground stations and to determine the percentages of observation time of any given celestial direction including Sun, Moon, Earth and Ground Stations constraints. The orbits considered can be elliptical and account is taken of the drift due to the Earth's oblateness.     

Soft X-ray emission from radio Loops I and III compared

We examine X-ray maps of the whole sky covering energies from 0.1 to 6 keV. We model Loop I X-ray emission as being caused by an old supernova that exploded into an already warm interstellar medium. After comparison with Loop III we deduce that there may be a general temperature gradient in the gas as we move away from the plane in the northern galactic hemisphere.     

Mean winds of the mesosphere and lower thermosphere (60–110 km): A global distribution from radar systems (MF,Meteor, VHF)

During the last decade a large number of radars (～12) have been developed, which have produced substantial quantities of tidally-corrected mean winds data. The distribution of the radars is not global, but many areas are well covered: the Americas with Poker Flat (65°N), Saskatoon (52°N), Durham (43°N), Atlanta (34°N), Puerto Rico (18°N); Europe with Kiruna (68°), Garchy (47°N) and Monpazier (44°N); and Oceania with Christchurch (44°S), Adelaide (35°S), Townsville (20°S), and Kyoto (35°N). Zonal and meridional wind height-time cross-sections from $\text{60}\text{80}$ km (MF/Meteor Radar) to ～110 km have been prepared for the last 5–6 years. They are compared with cross-sections from CIRA-72 for zonal winds, and Groves (1969) for meridional winds.It is shown that while CIRA-72 is still a useful model for many purposes, significant differences exist between it and the new radar data. The latter demonstrate important seasonal, latitudinal, longitudinal and hemispheric variations. The new meridional cross-sections are of great value. The common features with Groves (1969) are the equatorward cells in summer near 85 km; however their strength (～10 ms^?1) and size are less. Systematic and somewhat different variations emerge at higher (?52°N) and middle (35–44°) latitudes.     

A new polyethylene balloon film

After over twenty years there is a new film introduced in the United States for fabricating scientific balloons. The film was developed by Raven and is designated Astrofilm.The film is a result of a critical selection of both the resin and extruding parameters. The film's physical properties and results of a test flight are reported. Also reported are a proposed design modification and failure analysis.