Plasma sheet oscillations and their relation to substorm development: Cluster and double star TC1 case study

We examined two consecutive plasma sheet oscillation and dipolarization events observed by Cluster in the magnetotail, which are associated with a pseudo-breakup and a small substorm monitored by the IMAGE spacecraft. Energy input from the solar wind and an associated enhancement of the cross-tail current lead to current sheet thinning and plasma sheet oscillations of 3–5 min periods, while the pseudo-breakups occur during the loading phase within a spatially limited area, accompanied by a localized dipolarization observed by DSP TC1 or GOES 12. That is, the so-called “growth phase” is a preferable condition for both pseudo-breakup and plasma sheet oscillations in the near-Earth magnetotail. One of the plasma sheet oscillation events occurs before the pseudo-breakup, whereas the other takes place after pseudo-breakup. Thus there is no causal relationship between the plasma sheet oscillation events and pseudo-breakup. As for the contribution to the subsequent small substorm, the onset of the small substorm took place where the preceding plasma sheet oscillations can reach the region.     

Sulfur “concrete” for lunar applications – Sublimation concerns

Melting sulfur and mixing it with an aggregate to form “concrete” is commercially well established and constitutes a material that is particularly well-suited for use in corrosive environments. Discovery of the mineral troilite (FeS) on the moon poses the question of extracting the sulfur for use as a lunar construction material. This would be an attractive alternative to conventional concrete as it does not require water. However, the viability of sulfur concrete in a lunar environment, which is characterized by lack of an atmosphere and extreme temperatures, is not well understood. Here it is assumed that the lunar ore can be mined, refined, and the raw sulfur melded with appropriate lunar regolith to form, for example, bricks. This study evaluates pure sulfur and two sets of small sulfur concrete samples that have been prepared using JSC-1 lunar stimulant and SiO₂ powder as aggregate additions. Each set was subjected to extended periods in a vacuum environment to evaluate sublimation issues. Results from these experiments are presented and discussed within the context of the lunar environment.     

Certain approaches to the development of on-board automated training system

Perspectives of long-term space programs make it necessary to develop autonomous computer expert system for crew-members physical state control. The purpose of the work--to develop a set of objective formalizable physiological indices of working capacity suitable for reliable algorithmization of physical state control. Investigations were performed in on-earth microgravity simulation (3- and 7-day dry immersion, 6 subjects; 4-month antiorthostatic hypokinesy, 10 subjects) with volunteers' participation as well with 34 members of MIR-station expeditions during flights. Model exercise investigations were made also with 20 young male volunteers to evaluate the validity of different physical state indices. A set of indices was found which, being simple enough for measuring, performs to get satisfactory adequate evaluations of current organism physical state in long-term real or simulated microgravity. It was proved that some ergometric indices along with heart rate derivatives could reflect real working ability even better than traditional characteristics of organism energy systems state.     

Gated Phase-Locked Loop Study

The objectives of this paper are threefold. The first is to obtain a sampled data model of a gated phase-locked loop. Data from measurements made on an actual loop constructed in the laboratory are included, and the good agreement between measured and calculated results serves as a verification of the model. Second, with the aid of the model, some of the basic operating properties of the system will be presented. Third, comparisons will be made between gated and continuous loop operation.     

Modeling and simulation of spacecraft power systems

Modeling of a complete spacecraft power processing system is presented, using the Boeing EASYS software. Component models are developed, and several system models including a solar array switching system, a partially shunted solar system, and cosmic background explorer (COBE) system are simulated. The modes of operation of the power system, such as shunt mode, battery-charge mode, and battery-discharge mode, are simulated for a complete orbit cycle     

Probability Density of the Maximum Likelihood Elevation Estimate of Radar Targets

The probability density of the maximum likelihood estimate of elevation angle of a radar target in the presence of multipath is calculated. For detectable signals that have low signal-to-noise ratios, the density is a mixture of a Gaussian density and a delta function at the horizon.     

Cold resistance and metabolic activity of lichens below 0°C

Laboratory measurements show that lichens are extremely tolerant of freezing stress and of low-temperature exposure. Metabolic activity recovered quickly after severe and extended cold treatment. Experimental results demonstrate also that CO₂ exchange is already active at around −20°C. The psychrophilic character of polar lichen species is demonstrated by optimum temperatures for net photosynthesis between 0 and 15°C. In situ measurements show that lichens begin photosynthesizing below 0°C if the dry thalli receive fresh snow. The lowest temperature measured in active lichens was −17°C at a continental Antarctic site. The fine structure and the hydration state of photobiont and mycobiont cells were studied by low-temperature scanning electron microscopy (LTSEM) of frozen hydrated specimens. Water potentials of the frozen system are in the range of or even higher than those allowing dry lichens to start photosynthesis by water vapor uptake at +10°C. The great success of lichens in polar and high alpine regions gives evidence of their physiological adaptation to low temperatures. In general lichens are able to persist through glacial periods, but extended snow cover and glaciation are limiting factors.     

The Voyager infrared spectroscopy and radiometry investigation

The infrared investigation on Voyager uses two interferometers covering the spectral ranges 60–600 cm^–1 (17–170 m) and 1000–7000 cm^–1 (1.4–10 m), and a radiometer covering the range 8000–25 000 cm^–1 (0.4–1.2 m). Two spectral resolutions (approximately 6.5 and 2.0 cm^–1) are available for each of the interferometers. In the middle of the thermal channel (far infrared interferometer) the noise level is equivalent to the signal from a target at 50 K; in the middle of the reflected sunlight channel (near infrared interferometer) the noise level is equivalent to the signal from an object of albedo 0.2 at the distance of Uranus.For planets and satellites with substantial atmospheres, the data will be used to investigate cloud and gas composition (including isotopic ratios), haze scale height, atmospheric vertical thermal structure, local and planetary circulation and dynamics, and planetary energy balance. For satellites with tenuous atmospheres, data will be gathered on surface and atmospheric composition, surface temperature and thermal properties, local and global phase functions, and surface structure. For Saturn's rings, the composition and radial structure, particle size and thermal characteristics will be investigated. Comparative studies of the planets and their satellite systems will be carried out.Paris Observatory.Cornell University.Jet Propulsion Laboratory.University of Maryland.     

Observations of substorm-associated particle-flux variations at 6⩽L⩽8 with GEOS-1

Measurements made with the charged particle spectrometer of the Max-Planck-Institut für Aeronomie onboard GEOS-1 were used to investigate the behaviour of energetic electrons and ions in the dusk sector of the magnetosphere. During substorms the integral ion flux ( 24 KeV) increased whereas the integral electron flux ( 20 KeV) first decreased and later on also increased. The dependences of these flux variations on pitch-angle and particle energy are described and discussed in terms of particle drift in the geomagnetic and geoelectric fields and adiabatic energy variations. The results also provide some information on the source region of the drifting particles.