A high-altitude barium radial injection experiment

On 16 March 1980 a rocket launched from Poker Flat, Alaska, carried a new type of high-explosive barium shaped charge to 571 km, where detonation injected a thin disk of barium vapor with high velocity nearly perpendicular to the magnetic field. The purpose of the experiment, named “King Crab,” was to advance knowledge of the instabilities, waves, and optical and magnetic effects produced. The TV images of the injection are spectacular, revealing three major regimes of expanding material which showed early instabilities in the neutral gas. The most unusual effect of the injection is a peculiar rayed barium-ion structure lying in the injection plane and centered on a 5 km “black hole” surrounding the injection point. Preliminary computer simulations show a similar rayed structure development due to an electrostatic instability.     

Quasi-parallel collisionless shocks

The magnetic field and plasma data from the ISEE 1, 2, and 3 spacecraft have greatly increased our knowledge of the quasi-parallel collisionless shock in space. Hybrid-code simulations have provided us with valuable insights into the physics of the quasi-parallel shock. Unfortunately, theoretical understanding of the nonlinear physics of the quasi-parallel shock is still in a qualitative stage of development. Generation of large-amplitude whistler waves and hydromagnetic waves observed in the quasi-parallel shock has been discussed either in terms of linear instabilities or qualitative nonlinear arguments. It appears that the ion reflection, ion heating, and leakage of the shock-heated downstream ions at the quasi-parallel shock can all be explained in terms of nonadiabatic scatterings of ions by the large-amplitude whistler-magnetosonic waves with frequencies near the ion gyrofrequency and wavelength near the ion inertial length. The nonadiabatic scattering is defined by the non-conservation of the magnetic moment. Future study of the quasi-parallel shock should focus on developing quantitative theoretical models for the nonlinear physical processes fundamental to the quasi-parallel shock.     

Passive Array Tracking of a Continuous Wave Transmitting Projectile

Differential Doppler measurements by a passive array are used to track an unstable continuous wave (CW) source moving in a ballistic trajectory, e.g., a projectile carrying a proximity fuse. The ballistic equations of motion couple frequency measurements at various sections along the track with the track parameters at any arbitrary time, e.g., at impact. A nonlinear weighted leastsquare method is used to estimate the track parameters, and the resulting error covariance matrix is derived. A numerical example demonstrates the relative contributions of various frequency measurements to the estimation accuracy.     

Distributions of Radar Angels

A foremost characteristic of large dot radar angels is the wide variation of basic parameter values which they exhibit. This variation is traceable to the nature of the underlying phenomena, i.e., birds and flocks of birds. In this paper, statistical distribution models for the mean radar cross section (RCS) and density of radar angels are obtained, based on a combination of radar and direct ornithological data. The radar cross-section distribution model has been derived from a dimensionless RCS versus wavelength model for individual birds, obtained from measured RCS data which have been scaled to a dimensionless form. This model is applied to ornithological data on populations of birds. The density distribution model is based on statistical reduction of migratory bird data obtained by Lowery's moon watching experiment, and observed seasonal and diurnal variations of radar angel activity. Both resulting distribution models are closely appproximated by the log-normal distribution. The model parameters for these distributions are given.     

Advanced pointing systems for space astronomy

Requirements on image stability are increasing, often at the same time that instrument external disturbances are increasing. Pointing large diameter optics from the shuttle bay is the prime current example of this situation. In order to achieve cost-effective advanced pointing systems in the face of these problems, a system approach must be taken that encompasses a realistic assessment of requirements, the best possible detector technology, and a broad look at space vehicles and pointing systems that are available. As an example, a rocket instrument for making measurements of the interstellar gas uses a standard pointing system to achieve a spectral resolution of 2 × 10⁵.     

Flare buildup in X-rays,UV, microwaves and white light

Coordinated observations using space and ground-based instruments were made of active region complex #2522/2530, 24–30 June, 1980. The 10 largest flares from these regions were of importance M1-M6 in X-rays, and all were observed from satellites, except for one observed from a balloon. Several kinds of buildup signature have been found in the tens of minutes before these flares. Among these signatures are the following: 1) Relative faintness in X-ray lines of the pre-flare pixels, 2) X-ray (5–15 keV) “flashes” at points displaced by 1′–2′ from the flare site, 3) Rising filaments seen in Hα and Ultraviolet 4) Microwave intensification, polarization increase and polarization flip 5) Coronal disturbances above limb flares at or before the impulsive phase.     

270-VDC/hybrid 115-VAC electric power generating system technologydemonstrator

The approach, system architecture, instrumentation, and performance of a technology demonstrator system for the application of 270-VDC/hybrid 115-VAC electrical power generation and distribution to future military aircraft are examined. The design has focused on assembling a highly flexible test system. The loads are typical of those in a hybrid electrical system. The system consists of a single 3-phase, 115-VAC electrical generator whose output is rectified, filtered, and supplied through DC contactors to both a 270-VDC load bus and to the input of an inverter, which supplies a 400-Hz, 115-VAC load bus. A variable-frequency, 115-VAC bus is also available directly from the generator. A prototype variable-speed constant-frequency 120-kVA generator is used. The test facility is designed to provide loads to all power types capable of being produced by the system. The system has provided particularly good insight into various aspects of 270-VDC/115-VAC hybrid systems and their components     

A surge obsrved in Hα and CIV

Simultaneous Hα (MSDP at Meudon) and C IV (UVSP aboard SMM) measurements of Active Region 2701 were made on October 2, 1980. Isodensity and velocity maps were derived for both lines and superposed. A good correlation was found between Hα and C IV velocities. A surge was observed for 10 minutes. The base was located in a bright point in CIV and Hα, and escaping matter followed the same channel (“absorbing” in Hα, “emitting” in C IV). The velocity along the surge was about 80 kms.-1 in Hα and 100 km s-1 in C IV. A loop appeared in C IV. We discuss the existing models and conclude that the vertical pressure gradient was capable of driving the surge.     

False Alarm Rate and False Alarm Number for Discrete and Continuous Time Sampling

A comparison of the false alarm rates and false alarm numbers for discrete and continuous time sampling is given for different noise spectrums (rectangular, Hamming, Gaussian, and cosine noise voltage spectrums) and for different sampling rates for the case of discrete time sampling. Also given is the increase in the false alarm rate when going from discrete to continuous time sampling when the detection threshold is held fixed. The amount that the threshold has to be increased for continuous sampling to achieve the same false alarm rate obtained with discrete time sampling is also given.     

How important are changes in body weight for mass perception?

It is often assumed that weight judgements depend primarily on the effort experienced in lifting an object against a 1-G force. Changes in effort and in other weight-cues certainly alter apparent heaviness; but there is a tendency towards mass-constancy when such changes are unrelated to mass. Under water or altered G, both the observer's body and other objects change their effective weight: the change in the former probably provides a cue to the latter. Mass-constancy increases with opportunity for adaptation to the change, leaving a negative aftereffect on return to normal circumstances. The discrimination of weight or mass also deteriorates with sudden changes in arm weight, just as it does with other types of maladaptation and with a reduction in sensory cues. The relative importance of arm weight and other factors has not been precisely measured, but experiments in prolonged spaceflight should help to elucidate the issue.