An approximation of the height of the O+ - H+ transition level for use in IRI

A set of data including over 1400 transition level (TL) encounters of the OGO-6 satellite is used to construct analytical presentations of this altitude upon dip-latitude and longitude. The formula represents the TL variation between ± 50° dip-latitude and 20 h and 04 h local time interval. The data were obtained in the high solar activity period in 1969 and 1970.     

Adaptive Array Bandwidth with Tapped Delay-Line Processing

The bandwidth of adaptive arrays with tapped delay lines behind the elements is examined. Such processing offers improved bandw over that attainable with quadrature hybrid processing. The performance of a two-element array with four types of processing (equarature hybrids, single delay lines, 3-tap delay lines, and 5-tap delay lines) is compared. It is shown that with half-wavelength element spacing, a quadrature hybrid and single delay-line processor are inadequate at 10-percent bandwidth. A 3-tap processor is adeq however, up to 40-percent bandwidth.     

Comparative analysis of chemical composition and optical properties of gaseous and disperse phases of the Earth-group planetary atmospheres

The models of chemical composition and structure of the Earth-type planetary atmospheres are offered. The optical properties of gaseous and disperse phases of the atmospheres are investigated.     

The microlesion concept in HZE particle dosimetry.

High energy, high-Z (HZE) particles are present in high-altitude and high-inclination satellite orbits. Most of the HZE dose above LET = 200 keV/micrometer is due to Fe nuclei. Individual HZE particles can damage several cells adjacent to one another along the particle track in tissue. The outcome has been described as a "microlesion" by D. Grahn. The present study attempts to define conditions for microlesions in specific tissues, to seek biological evidence that microlesions are produced, and to evaluate the microlesion as a potentially useful unit of dose in assessing hazards to spaceworkers. Microlesions in individuals cells and hair follicles have been described. Microbial studies have provided some evidence for independent secondary electron action. Whether or not a few hundred microlesions would be damaging to the whole organism depends upon the nature of damage to critical tissues. For example, cancer may occur if microlesions kill several cells in a straight line and mutate other cells alongside the particle track. Fe particle irradiation of the mouse Harderian gland (Fry et al., this issue) produces tumors efficiently. Microlesions in the lens, cornea, and retina need to be considered. Further dialogue is required before a final decision can be made concerning the most appropriate way to assess the HZE hazard.     

Superclustering of galaxies and X-ray sources

An attempt is made to compare optical properties of Abell clusters with X-ray sources.     

GPS Aided Inertial Navigation

The Global Positioning System is an extremely accurate satellite-based navigation system which, after its completion in 1989, will provide users worldwide, 24 hour. all weather coverage. A joint research project among Boeing, Rockwell-Collins, and Northrop has been completed in which a GPS receiver was integrated with a low-cost strap-down inertial navigation system and a flight computer. A Kalman filter in the latter allows in-fight alignment and calibration of the INS. In addition, feedback from the INS to the GPS receiver improves the system's ability to reacquire satellite signals after outages. The resulting system combines the accuracy of GPS with the jamming immunity and autonomy of inertial navigation. System tests were conducted in which a Boeing owned T-33 jet aircraft was flown through known test pattern to align and calibrate the INS. Earlier tests, including tests against an airborne jammer, were conducted in a modified passenger bus.     

Perturbation solutions for variable energy blast waves

The trajectory of and the flow field behind blast waves with time varying energy input is determined. Freeman's (1968) Lagrangean coordinate formulation is modified to include both the geometric factor, α, for plane, cylindrical and spherical shocks and also non-integer values of β, the energy input parameter, in a single computational algorithm. Numerical problems associated with vanishing density at the inner mass boundary or “piston face” are then examined and solved. Second order perturbation solutions about the solution for an infinite strength shock are then obtained in Sakurai's (1965) inverse shock Mach number expansion parameter for 0 β < α + 1. Tables and graphs of significant numerical coefficients are presented for comparison to, and extension of, results of other authors. Graphs of typical shock trajectories and flow field density, pressure and velocity variations are also presented and discussed.     

The structural features of the germanium-silicon solid solution crystals obtained under microgravity

Structural features of germanium-silicon solid solution crystals have been investigated and silicon distribution in the crystals has been studied. All the crystals obtained under microgravity had, in spite of good external shape and facetting, a poorer internal structure than those obtained on Earth. The distribution of silicon have been shown to be non-uniform. High dislocation densities were observed.     

Minimum Number of Satellites for Three-Dimensional Continuous Worldwide Coverage

Global positioning by means of satellites requires simultaneous observation by at least four satellites. The problem is to determine the minimum number of satellites and the corresponding orbital geometry necessary to satisfy this requirement on a continuous basis. To model the problem, a fixed number of users are assumed uniformly distributed in a known manner over the surface of the earth, and the satellites are restricted to exist in either three or four orbital planes. However, the orbit radius and inclination angle are left as variables. Under these assumptions, and starting with a small number of satellites which will be increased afterwards, an algorithm is developed to determine the visibility of satellites at each surface location. In this way it is possible to specify the minimum number of satellites needed by any desired orbital geometry. It is found that the number of satellites required for three-dimensional continuous worldwide coverage decreases as the orbit radius is increased. There appears to be no general trend regarding the effect of the inclination angle on the minimum number of satellites.     

Interference Immunity Effects in CPSK Systems with Hard-Limiting Transponders

Transmission characteristics are described for M-ary coherent phase-shift keyed (CPSK) systems with N-stage hard-limiting transponders where noise and multiple continuous wave (CW) interference sources are additively combined in each link. A general expression for the probability density function of the composite phase at the final link is derived; the overall error probability is then obtained from this general expression. Comparisons with N-cascaded linear amplifier systems clearly show the noise and interference immunity that result from the use of bandpass hard limiters (BPHLs). The BPHL system's error probability improvement versus interference sources is shown to be much larger than the improvement versus noise.