Pulsar studies with GRO-COMPTEL

Pulsar measurements performed by the experiment COMPTEL, aboard the Compton Gamma Ray Observatory, are described. The main results refer to the Crab and Vela pulsars whose pulse shape characteristics are given in some detail and light curves are compared with those above 50 MeV, as observed by the COS-B satellite. No other gamma-ray pulsars have been detected to date by COMPTEL, the upper limit on the pulsed signal from Geminga being compatible with indications by other experiments.     

Stigmatic bragg crystal spectrometers for cosmic X-rays

Two instruments, one a large free-standing self-focusing spherical array and the other a small cylindrical crystal used at the focus of a large grazing incidence x-ray collector, are discussed. Both instruments offer several advantages over more conventional spectrometers, i.e., mechanical simplicity, moderate resolving power (10²), and good sensitivity.     

The Generation of Correlated Weibull Clutter for Signal Detection Problems

A method is discussed for generating Weibull vectors with a desired correlation matrix and specified parameters. Such vectors may represent samples of a correlated clutter signal. The presented method makes use of a suitable nonlinear transformation of random Gaussian vectors with correlated components. Computational aspects of the method are also discussed.     

Microprocessor-Controlled Digital Shunt Regulator

A new approach to the design of power systems is presented in which a microprocessor is used as a controller for a digital shunt regulator (DSR). This approach meets the demands of future space and ground missions, i. e., high efficiency, high reliability, low weight, low volume, increased flexibility, and less development time. This approach responds to future demands by permitting realtime modification of system parameters for system optimization. This feature is especially important in the event of an anomaly. As the microprocessor need not be dedicated to the DSR, it can simultaneously be used for battery management and for charge regulator/discharge regulator control. This approach also reduces the component count, simplifies assembly and testing of the unit, results in significant time saving, and increases the reliability.     

Problems in the analysis of gamma-ray burst spectra

Spectral measurements by the Solar Maximum Mission have been used to confirm the cyclotron lines in gamma-ray bursts reported from the Konus experiment. We present ISEE-3 data for the same burst (GB800419) during the same period of time which show no line. We discuss various problems in the analysis of scintillator spectra and point out that unfolded spectra are not necessarily unique and that the position of a data point in a deconvolved spectrum may vary depending on the assumed overall shape of the spectrum. As a result, if the analysis assumes a soft spectrum (such as optically thin thermal bremsstrahlung) an absorption feature might appear, whereas a harder spectrum (such as a Comptonized blackbody) would not require the feature. Since the continuum shape probably changes during the duration of a typical burst, the nonuniqueness of the spectral unfolding, combined with the assumption that the continuum is optically thin thermal bremsstrahlung, could give rise to spurious “absorption” features which vary on a time scale of seconds. Despite these problems, there is still some evidence for $\text{narrow}$ spectral lines in the range 45 to 65 keV but not for the broad lines reported from the Konus experiment. Unfortunately, the range 45 to 65 keV is the most difficult spectral region to unfold.     

Selected examples of profitable applications of remote sensing for resources inventories and monitoring

The Remote Sensing Centre of the Institute of Geodesy and Cartography in Warsaw has been operating since 1976. It has multi-disciplinary character; carries out scientific research, elaborates technologies of remote sensing investigations, applies remote sensing methods for solving various practical problems, coordinates national activities in this field, developes and disseminates remote sensing knowledge at both national and international levels offering various types of specialized training.The authors discuss the role of remote sensing investigations in the process of development planning. Examples of projects executed at the Remote Sensing Centre and concerning topographic and land use mapping, geological investigations, agricultural crop area determination, forest research, environmental monitoring and studies of climatic conditions in urban environment are described and extensively discussed in the paper. The authors emphasize these areas of the application of remote sensing and these interpretation techniques which are of potential interest for the developing countries.     

Lightweight (AlGaAs)GaAs/CuInSe2 tandem junction solarcells for space applications

Mechanically stacked tandem cells consisting of GaAs thin-film upper cells and CuInSe₂ thin-film lower cells have been developed to meet the increasing power needs projected for future spacecraft. The authors report the fabrication of the first highly efficient lightweight GaAs/CuInSe₂ tandem cell on a 2-mil thick substrate, update recent performance improvements in thin-film GaAs/CuInSe₂ tandem cells, and discuss their application to space power systems. The efficiency of 4-cm² cells has improved to 21.6% AM0, the highest ever reported for a thin-film photovoltaic cell. Lightweight 4-cm² tandem cells have been successfully fabricated with efficiencies as high as 20.8%. These cells weighed about 180 mg without optimized substrate trimming. Radiation and operating temperature effects on GaAs/CuInSe₂ tandem cells are also discussed, and an interconnect scheme to form a voltage-matched string is described     

Determining rotation rates from light curves: RW Mon and RW Tau

We present light curve solutions for the non-synchronously rotating Algols RW Mon and RW Tau, and we illustrate how rotation rates are determined from light curves. We find RW Mon's primary component to spin at about 5 times the synchronous rate, which confirms the indication of fast rotation from reported emission line activity. RW Tau turns out to be only a mildly rapidly rotating Algol system, and our light curve solutions do not yield any firm value for the rotation rate of the primary component. It is suggested that continued efforts should be made to do good quality line broadening studies in order to find rotation rates for systems with only modest degrees of rapid rotation, and in order to further test photometric rotation rates against those of line broadening studies.     

LIPS III-a solar cell test bed in space

The LIPS III satellite, which was launched into a 1100-km circular orbit of 60° inclination in the spring of 1987, is discussed. LIPS III is a member of the living-plume-shield class of spacecraft, all of which were built around a simple sheet metal plume deflector. The purpose of LIPS III was to provide a testbed for space power sources. An overview of the LIPS III system is given, and the experiments submitted for it, all but one of which were photovoltaic in nature, are described     

International participation and the space station : A contractor's perspective

This article presents the views of the Boeing company on the benefits and disadvantages of international participation in the space station. The author outlines the company's goals within the project, and makes some recommendations on how to reduce the concerns which arise from international cooperation, in order to maximize the benefits which could be achieved.