First results of the growing of PbTe single crystals under microgravity conditions

Two sublimation experiments with PbTe were performed at 850°C and 750°C under microgravity conditions during the “Salyut-6”-“Soyuz-31” mission in 1978. The sublimation took place on the (100)-face of a PbTe crystal. The condensate grown at 850°C shows in the upper part the formation of a pyramidal habit. The bulk consists of parallel growth colums with [100]-boundary faces. The charge carrier concentration of the electrons (N=1,5·10¹⁹ cm^?3) is higher than the homogeniety limit for 800°C should permit. This is in contrast to the result obtained on the PbTe crystal of the parallel experiment on the earth. At 750°C a laminated condensate is grown with a low growth rate. The microphotograph of the substrate shows the beginning whisker formation according to the VLS-mechanism.     

Magnetic coordinates

The definitions and properties of the magnetic coordinates B, L, K, ₀, R, and are reviewed. The roles these parameters play in the study of geomagnetically trapped particles are discussed in detail. The intrinsic accuracy of the magnetic shell parameter L is examined as are the accuracies which are desired, available, and possible. A plea is made for the adoption of standard methods of presenting results.Paper presented at Advanced Study Institute of IIT Research Institute, Bergen, Norway, August 16 1965.     

Bioinstrumentation for evaluation of workload in payload specialists: results of ASSESS II

ASSESS II (Airborne Science/Spacelab Experiments System Simulation) was a cooperative NASA-ESA project which consisted of a detailed simulation of Spacelab operations using the NASA Ames Research Center CV-990 aircraft laboratory. The Medical Experiment reported on in this paper was part of the complex payload consisting of 11 different experiments. Its general purpose was to develop a technology, possibly flown on board of Spacelab, and enabling the assessment of workload through evaluating changes of circadian rhythmicity, sleep disturbances and episodical or cumulative stress. As parameters the following variables were measured: Rectal temperature, ECG, sleep-EEG and -EOG, the urinary excretion of hormones and electrolytes. The results revealed evidence that a Spacelab environment, as simulated in ASSESS II, will lead to internal dissociation of circadian rhythms, to sleep disturbances and to highly stressful working conditions. Altogether these effects will impose considerable workload upon Payload Specialists. It is suggested that an intensive pre-mission system simulation will reduce these impairments to a reasonable degree. The bioinstrumentation applied in this experiment proved to be a practical and reliable tool in assessing the objectives of the study.     

Outer space exploitability: International law and developing nations

This article outlines the principles upon which international space law is based. Space law has been successful so far in benefiting the developing countries without hampering the spacefaring nations. The principal treaty provisions that are of special interest to developing nations are discussed, and issues associated with remote sensing, communications and environmental harms are examined in detail. Since 1967 there has been a sharp change in the focus of legal concern towards ‘taking into account the particular needs of developing countries’, a principle that will be central to arrangements for the equitable sharing of the benefits of exploiting the space environment and its natural resources.     

Victor A. Brumberg and Eugene V. Brumberg,Celestial Dynamics at High Eccentricities

Space Science Reviews -     

Operation and performance of a second generation, solid state, star tracker, the ASC

The Advanced Stellar Compass (ASC) is a second generation star tracker, consisting of a CCD camera and its associated microcomputer. The ASC operates by matching the star images acquired by the camera with its internal star catalogs. An initial attitude acquisition (solving the lost in space problem) is performed, and successively, the attitude of the camera is calculated in celestial coordinates by averaging the position of a large number of star observations for each image. Key parameters of the ASC for the Ørsted satellite and Astrid II satellite versions are: mass as low as 900 g, power consumption as low as 5.5W, relative attitude angle errors less than 1.4 arcseconds in declination, and 13 arcseconds in roll, RMS, as measured at the Mauna Kea, HI observatories of the University of Hawaii in June 1996.