Altitude Damping of Space-Stable Inertial Navigation Systems

In order to stabilize the altitude calculation in an inertial navigation system, an altimeter is commonly used. In a conventional local-level mechanization, this is generally accomplished by correcting the vertical channel integrators with the difference between the inertial system and altimeter indication of vertical position. However, in a space-stable system the procedure is not as clear since a vertical channel is not physically present. Three altitude damping mechanizations for a space-stable inertial navigation system are proposed. The equivalent local-level mechanizations are then found by comparing error propagation equations in a common coordinate frame.     

Constant-False-Alarm-Rate Processors for Locally Nonstationary Clutter

A technique for designing normalizing processors for locally non-stationary clutter is discussed. The design procedure assumes the logarithm of the clutter power varies as a polynomial with range. When the actual environment matches the design environment, the false-alarm rate is a constant that is independent of the polynomial coefficients. A measure of the relative target detection capability as a function of the number of normalization cells and the degree of the design-environment polynomial is given. The applicability of the processors to non-Rayleigh clutter is discussed.     

Cross Polarization in Radomes: A Program for Its Computation

A study is made of transmission by radomes, with particular reference to cross polarization, and of the consequent radiation patterns of the radome with its aerial for both linear and circular polarizations. The work is embodied in a computer program which considers a scanner of specifiable size, position, and power distribution at different orientations inside a multilayer radome of given dimensions, class of shape, and construction in terms of the number and properties of its layers. Initially, rays are traced from points on the scanner, and details of their paths and propagation are presented in tables of preliminary results; later, diffraction theory is used. Polar diagrams of cross polarization, of main beam, etc., are presented in final tables for the system. Nearly all the parameters are specifiable, and so the program has reasonably general applicability, and it can also assess the effects of bandwidth, tapering of layer thickness, complex permittivity, and other parameters of the system.     

Performance Degradation Due to Specular Multipath Intersymbol Interference

Plots of performance degradation are used to compare the effects of fading and intersymbol interference in a two- component specular multipath digital communications channel. Similar plots are then used to compare two practical receivers designed to combat the interference. Degradation plots are shown to allow easy identification of each receiver's range of usefulness, as well as identification of variance bounds demanded of channel parameter estimates which the receivers require.     

Biological effects of heavy ions from the standpoint of target theory.

The biological effect of heavy ions is best described through the action cross section, as a function of the end-point of interest and the charge and speed of the ion. In track theory this is called the "ion-kill" cross section, for it is the effect produced by a single heavy ion and its delta rays. As with nuclear emulsions the biological track structure passes from the grain count regime to the track width regime to the thindown region with an increase in LET. With biological cells, as with any detector capable of storing sublethal damage, with low LET irradiation the action cross section (in the ion-kill mode) is increasingly obscured by the effect of "gamma-kill", by the influence of overlapping delta rays from neighboring heavy ions. Thus at low LET response is dominated by the gamma-kill mode, so that the RBE approaches 1. The theory requires 4 radiosensitivity parameters for biological detectors, extracted from survival curves at several high LET bombardments passing through the grain count regime, and at high doses. Once these are known the systematic response of biological detectors to all high LET bombardments can be unfolded separating ion kill from gamma kill, predicting the response to a mixed radiation environment, and predicting low dose response even at the level of a single heavy ion. Cell killing parameters are now available for a variety of cell lines. Newly added is a set of parameters for cell transformation.     

Formation and evolution of low-mass Algols

We discuss the origin, evolution and fate of low-mass Algols (LMA) that have components with initial masses less than 2.5 M₀. The semi-major axes of orbits of pre-LMA do not exceed 20–25 R₀. The rate of formation of Algol-type stars is 0.01/year. Magnetic stellar winds may be the factor that determines the evolution of LMA. Most LMA end their lives as double helium degenerate dwarfs with M₁/M₂ 0.88 (like L870-2). Some of them even merge through angular momentum loss caused by gravitational waves.     

An Electrooptical Automatic Gain Control

The laser beam affords a valuable carrier medium for an optical calmunication system, but such a system for transmission through the atmosphere is subjected to wide fluctuations in received signal strength because of turbulence. An electrooptical automatic gain control system em has been studied and built which can substantially reduce the effect of these fluctuations. The effect of system parameters on the control characteristics are considered.     

X-ray and optical observations of Nova Muscae 1983 during its nebular stage

The detection of X-rays from Nova Muscae 1983 (discovered on January 18, 1983) constitutes the first detection of X-rays from a classical nova during outburst. X-ray observations were carried out on 1984 April 20 and July 14 when Nova Mus had entered the nebular stage. During both observations no significant flux was observed with the medium energy detectors (2–50 keV). The source was detected with the low energy detector (.04–2 keV) using 3000 Å Lexan and Parlene- N-Aluminium filters; counting rates of (3.4 ± 1.2) × 10³ and (3.7 ± 1.2 × 10^-3 counts/sec were measured with the respective filters. The source was detected again on July 14 with about the same intensity. Either a shocked shell of circumstellar gas emitting 10⁷ thermal bremsstrahlung at 10³⁵ erg/sec intensity or a white dwarf remnant emitting 3.5 × 10⁵ blackbody radiation at 10³⁷ erg/sec luminosity are compatible with the measurements.Spectra taken in the visual spectral range show strong forbidden coronal emission lines of [FeVII] 6085, [FeX] 6374, and as never observed before in such a strength, [FeXIV] 5303 requiring excitation temperatures of 2 × 10⁶ °K.     

Conjugate features of magnetospheric electron dynamics observed at balloon altitudes

Analysis of recent observations (from balloons, spacecraft, and surface observatories) demonstrate regional, shell, and nearpoint conjugacy at L ～ 7 during precipitative events which were characterized by local acceleration as well as release of gradient-drifted electrons injected during substorms. A number of new features of magnetospheric dynamics relating to substorm development and sudden-commencement effects, have been brought to light which, though poorly understood at present, may prove of considerable importance and are worthy of further investigation.

1. During the initial period of instability in substorm evolution, preceding the slower magnetotail convective injection, precipitation of waves of electrons in rapid polewards motion exhibit L-shell conjugacy near midnight.
2. Transient, large scale expansions of the magnetospheric electron population accompanied by temporally imbedded substorms display large scale regional conjugacy and are simultaneously observed as similarly transient intensity dropouts at balloon altitudes.
3. Precipitation from gradient-drifting electrons in the dayside magnetosphere exhibits near point-conjugacy, at least down to the order of 50 km and quite probably less.

Similarly tight conjugacy applies to the release of electrons showing a specific local response to sudden commencements.

1. Analysis of the approach to and attainment of spectral equilibrium in the precipitation observed from drifting electrons may provide information about either, or both, the source spectrum at injection and the process of local release.
2. The specific precipitation effect sometimes observed at the time of an SC remains a rather puzzling feature, although it seems clear now that the acceleration and/or release process responsible is of a highly local nature and works selectively at small pitch angles well within the magnetospheric boundary. Coupling of the interplanetary shock with the magnetosphere must be an important aspect, but the details are not clear as yet.
3. On at least one occasion, a large part (perhaps all) of the magnetospheric electron population varied in a nearly synchronous manner in response to solar wind induced distortions during the variable compressive phase of a sudden commencement geomagnetic storm.

In the ongoing effort to identify and understand acceleration and release mechanisms involved in magnetospheric dynamics, balloon-borne experiments will continue to be useful, providing essential information presently unattainable by other means.