VLF waves: Conjugated ground-satellite relationships

The French mobile station for recording geophysical data has been put in operation at Husafell, Iceland (64°5N, 20°8W) between the 10th of July and the 22nd of September, 1977. This place was more or less conjugated with GEOS when this satellite was near its apogee. The equipments installed in the station for recording VLF and ULF phenomena have characteristics (band-pass, sampling rates) which are identical to the similar equipments installed onboard GEOS. Intercomparison between signals recorded at both points are therefore easy. We present here the results which were obtained in the VLF range.In many occasions, VLF emissions (mainly hiss) do present identical variations in amplitude, with a very abrupt (<1 mn) and very large (>20 dB) decrease in amplitude. Because of their simultaneity at both points, such abrupt variations cannot be interpreted in terms of a sudden ionospheric absorption (associated with an enhanced particle precipitation) nor in terms of a sudden crossing of detached plasma regions. In some cases, these abrupt changes in the VLF intensity are associated with the appearance and disappearance of strong ULF emissions, in the Pc-1 frequency range. Some examples of associated onboard measurements of high energy electron fluxes or cold plasma density (when available) are given, which may help understanding these VLF conjugated relationships.     

Successful Large-Scale Use of CMOS Devices on Spacecraft Traveling Through Intense Radiation Belts

This paper describes the environmental models of the radiation belts and computational techniques which have been developed for predicting the radiation hazards for spacecraft These data and techniques are then applied to the Atmosphere Explorer 51 spacecraft to explain its successful survival for more than 18 months in a severe environment In particular, the results of the analysis are used to explain the performance of sonm 2400 CMOS devices, and consequently, they demonstrate the reliability of this device technology gy in spacecraft systems.     

The astrophysics of Jupiter

We compare the properties of Jupiter with those of radio pulsars and find a number of parallels insofar as the magnetic field, energization, and radio emission properties (pulsed, coherent, and microstructured), as well as a number of important presumed differences such as the Io modulation. Now that we can directly explore Jupiter's magnetosphere (but are yet uncertain as to the exact source of its radio emissions) what we learn may help us understand pulsars and other inaccessible astrophysical objects.Proceedings of the NASA JPL Workshop on the Physics of Planetary and Astrophysical Magnetospheres.     

Technology-based design and scaling for RTGs for space exploration in the 100 W range

This paper presents the results of a study on design considerations for a 100 W radioisotope thermo-electric generator (RTG). Special emphasis has been put on designing a modular, multi-purpose system with high overall TRL levels and making full use of the extensive Russian heritage in the design of radioisotope power systems. The modular approach allowed insight into the scaling of such RTGs covering the electric power range from 50 to 200 W_e (EoL). The retained concept is based on a modular thermal block structure, a radiative inner-RTG heat transfer and using a two-stage thermo-electric conversion system.     

Shock wave/turbulent boundary layer interaction and its control

The interaction between a shock wave and a boundary layer often leads to extremely detrimental effects, especially if the shock is strong enough to separate the boundary layer. When this happens, there occurs a rapid growth of the dissipative region along with a dramatic intensifying of turbulent fluctuations with the frequent occurrence of buffeting. In the present review some fundamental properties of the interaction are first considered for a two-dimensional, adiabatic flow developing on a flat surface. The following features are first examined: upstream interaction length, incipient shock-induced separation and evolution of the boundary layer properties during the interaction process. Supersonic and transonic flows are both considered. In a second part, the means envisaged to control shock/boundary layer interactions are presented, with emphasis on the physics of phenomena involved in this process. Control methods can be classified into two categories: those acting on the boundary layer properties before it enters the shock region (e.g. wall cooling, wall mass transfer, upstream blowing) and those having a local action in the shock foot region itself (e.g. suction or injection, boundary layer removal, passive control). The most appropriate technique depends on the specific application under consideration. Finally, some calculation methods are briefly presented, most of them being restricted to laminar interactions.     

A European view on UNISPACE III follow-up

Preparations for the third UN Conference on the Exploration and Peaceful Uses of Outer Space (UNISPACE III) were intense. The conference itself was a success. But what forms will the follow-up take? Just reading the 150-page report is an effort in itself. Having played a central part in the preparations and organization, Europe fully appreciates the need to build on the spirit of cooperation which emerged from UNISPACE III. In November 1999, the European States gathered to analyze the results of the conference and to set a course for their future participation in the United Nations Programme on Space Applications (UNPSA), which is mainly done through ESA, and for their participation in the United Nations Committee on the Peaceful Uses of Outer Space (UNCOPUOS), which is done through coordination among ESA Member States. This article presents the authors’ personal accounts of the results of the European efforts around UNISPACE III and shows how ‘European foreign policy’ can work in international space policy. It also seeks to illustrate Europe's commitment to putting space technology to work for the benefit of development throughout the world.     

Governance of national space activities

Senior political and space agency personnel joined representatives of industry and other space-related institutions for a conference, held in Budapest in January 2009, on how best to structure national and European space governance. Four sessions examined the subject of the conference from a top-down European, a bottom-up national, a theoretical and actor-based and a discursive–participative perspective. The themes and outcomes of the conference are reported below.     

Modelling ionospheric vertical drifts over Africa low latitudes using Empirical Orthogonal functions and comparison with climatological model

For the first time, empirical model of daytime vertical $\mathbf{E}\times \mathbf{B}$ drift based on Empirical Orthogonal functions (EOF) decomposition technique is presented. Day-to-day variability of $\mathbf{E}\times \mathbf{B}$ drift inferred from horizontal (H) geomagnetic field data around dip latitude for the period of 2008–2013 is used to both develop and validate the model. Results show that the EOF technique is promising with modelled values and data giving correlation coefficient values of at least 0.90 for geomagnetic conditions of both $K_p?3$ and $K_p>3$ within 2008–2013. Independent model validation shows that in situ $\mathbf{E}\times \mathbf{B}$ values from ion velocity meter (IVM) instrument on-board C/NOFS satellite are closer to model $\mathbf{E}\times \mathbf{B}$ estimates than the climatological Scherliess-Fejer (SF) model incorporated within the International Reference Ionosphere (IRI).     

Towards a European vision for space exploration: Recommendations of the Space Advisory Group of the European Commission

As a result of increasing public and political interest in ‘space’ (i.e. solar system) exploration at the global scale, the Space Advisory Group of the European Commission has evaluated the situation in Europe with regard to its potential to participate in this ambitious global enterprise. Aspects of science, technology, environment and safety, society, spin-offs and international cooperation were all considered. The group concluded that Europe possesses sufficient key technologies and scientific expertise to play a major role in international space exploration and has recommended that the EU take a central role to ensure the success of future European space exploration, not only to give a clear political signal for the way forward but also to ensure an appropriate financial framework. In this way Europe would embrace the spirit of the European Space Policy and contribute to the knowledge-based society by investing significantly in space-based science and technology, thereby playing a strong role in international space exploration.     

ISDN Standards: Overview and Update

The Integrated Services Digital Network (ISDN) is currently evolving from its conceptualization by the CCITT international standards body to specification and implementation by network providers and equipment vendors. This paper provides an overview of ISDN standards that were approved by the CCITT in 1984, and identifies enhancements currently under study by the CCITT for 1988 approval.