TSS core equipment I.—Electrodynamic package and rationale for system electrodynamic analysis

Summary The first Tethered-Satellite System (TSS-1) Electrodynamic mission has been launched aboard the Space Shuttle STS-46 on July 31, 1992, as a joint mission between the United States and Italy. A 500 kg, spherical Satellite (1.6 m diameter), attached to the Orbiter by a thin (0.24 cm), conducting, insulated wire (Tether), has been reeled upwards from the Orbiter payload bay to a distance of 256 m, rather than the expected 20 km, when the Shuttle was at a projected altitude of 300 km. ASI, the Italian Space Agency, had the responsibility for developing the reusable Satellite, while NASA had the responsibility for developing the Deployer system and the Tether, integrating the payload and providing transportation into space. One of the main scientific goals of this first mission is to demonstrate the possibility of energy conversion from mechanical to electrical by using a long Tether orbiting through the Earth's magnetic field. ASI designed and developed an active experiment, referred to as Core Equipment, in order to carry out this demonstration, and to support all the scientific investigations related to the study of the TSS electrodynamic interactions with the Earth's ionosphere. The experiment uses two Electron Generator Assemblies (EGAs), located on the Orbiter, to re-emit into the ionosphere, as an electron beam, the electrons collected on the Satellite from the ionosphere. Other instruments provide current, voltage, and ambient pressure measurements, and allow, via a series of switches, different electrical configurations of the TSS. The Core Equipment was innovative for space experiments in general and Shuttle experiments in particular. In fact, it was the first flight in which the Shuttle has been used as an integral part of the experiment and not only as an observing platform. It was the first mission with an integrated approach to science, will all the instrumentation and their operative modes selected to characterize the electric properties of the TSS.     

EUV-FUV spectroscopy of TSS optical Phenomena

Summary We propose to use the IEH (International Ultraviolet Hitchhiker), a multidisciplinary facility (Astronomy, Solar System, Earth's atmosphere) to be mounted on the Shuttle pallet as a Hitchhiker flight opportunity, in order to obtain 2D images in the EUV-FUV ((400÷1300) ?) of the optical phenomena occurring in the neighborhood of the TSS satellite. These peculiar phenomena, not detectable during the first TSS mission, are primarily due to the interaction of a high-potential conductive body with the surrounding ionospheric plasma. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.     

The RETE experiment for the TSS-1 mission

Summary This paper describes the RETE (Research on Electrodynamic Tether Effects) experiment mounted on board the TSS (Tethered-Satellite System) satellite which was deployed on a cable from the space Shuttle Atlantis during the TSS mission flown in August 1992. The experiment layout and its modes of operation are described in detail. To give an idea of RETE capabilities and actual performance during the mission, samples of measurements are also presented.     

Laboratory simulation of the itneraction between a tethered satellite system and the ionosphere

Summary The authors report on the measurements performed in the IFSI/CNR plasma chamber at Frascati related to the laboratory investigation of the interaction between a plasma source and an ambient plasma of ionospheric type. Such an interaction is of relevant interest for the possibility of using electrodynamic tethered satellite systems, orbiting at ionospheric altitude, for generating electric power or propulsion in space. The interaction region was analysed at various conditions of ambient magnetic field ((0÷0.5) G) and at different polarization levels of the plasma source ((0÷40) V). The plasma measurements were carried out with a diagnostic system using an array of Langmuir probes movable in the chamber so that a map of the plasma parameters could be obtained at the different experimental conditions. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.     

The first Mission of the Tethered Statellite

Summary The first test flight of the Italian Tethered Satellite was carried out from July 31 to August 8, 1992 on board the Space Shuttle Atlantis. This paper, authored by one of the crewmembers, directly involved with the Tethered Statellite Mission, describes the on-board experiment environment and the Payload Crew experience. Paper presented at the 6th Cosmic Physics National Conference, Palermo, 3–7 November 1992.     

A model for the normal ionosphere over Rome

Summary Some results of statistical analyses on data from the Rome ionospheric station during the period 1948–1983 are shown as a model of the normal ionosphere over Rome.

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Riassunto Si presenta un modello della ionosfera normale su Roma ottenuto con l'analisi statistica dei dati provenienti dalla locale stazione ionosferica lungo il periodo 1948–1983.

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Резюме Предлагается модель нормальной ионосферы на Пимом на основе статистического анализа данных, полученных в Риме на ионосферной станциqi в течение 1948–1983 г.г.

     

Electromagnetic radiation from a conducting tether moving in the ionosphere

Summary We set up a model to compute electromagnetic radiation associated with the motion of a conductor through a magnetized plasma. Calculations are carried out, in the framework of cold-plasma theory, for radiation near the ion cyclotron frequency. Results are applied to the TSS (Tethered Satellite System) project presently under development.

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Riassunto S’imposta il formalismo generale per il calcolo della radiazione elettromagnetica associata con il moto di un conduttore in moto attraverso un plasma magnetizzato. I calcoli sono poi fatti specificamente per la radiazione nelle vicinanze della frequenza di ciclotrone degli ioni. I risultati sono applicati ai parametri del progetto spaziale TSS (Tethered Satellite System) che è attualmente in fase di sviluppo.

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Резюме Мы предлагаем модель для вычисления электромагнитного излучения, связанного с движением проводника через намагниченныю плазму. Вычисления проводятся в рамках теории холодной плазмы для изучения вблизи ионной циклотронной частоты. Полученные результаты применяются к ТСС (связанная система спутников), проект которой разрабатывается в настояцее время.

     

On some electromagnetic phenomena in the tether magnetoplasma cloud

Summary The tethered satellite system (TSS) will be accompanied by a variety of electromagnetic phenomena. An independent interconnected formation, a ?tethered magnetoplasma cloud? (TMC), moving in space along the orbit of TSS, at an altitude of about 300 km, will be created. This time-dependent cloud will be a very complicated inhomogeneous formation including electromagnetic oscillations and waves of different type. Some of these waves will be observed on the Earth's surface. Rarefiel regions of the magnetoplasma behind, and dense regions in front of the shuttle orbiter (SO) and the subsatellite (SS) will arise. The neutral nitrogen beam ejected by the thruster becomes an ion beam on the day-light part of the orbit. Its energy is much greater than the local thermal energy. Instabilities of different kind as well as diffusion and recombination effects are expected to accompany the interaction of these beams with the surrounding plasma. The electron beams will produce other types of instabilities. By the electrons precessing along the magnetic-field lines, a current (5·10³V, 0.5 A) should be induced in the 20th km length conducting tether. It will be closed at the bottom of the ionosphere. This huge magnetic loop, so-called ?phantom loop? (PL), should accompany the tether system along its orbit. The length of this ?tether electromagnetic tail? (TEMT) is about 200 km, its magnetic moment will be about 10¹³ A·cm². Alfvén waves and nonlinear effects of heating type may be produced by this loop along the magnetic-field lines. ?Strings? of hot plasma may accompany the tether system.     

Radiation from long conducting tethers moving in the near-earth environment

Summary In connection with the presently developed TSS (tethered satellite system) project, we consider the problem of radiation of electromagnetic waves from a long conducting tether moving in the ionosphere. In particular, we address to radiation of low-frequency plasma modes, from ULF up to the electron cyclotron frequency. Both the case of a passive tether (no generator) and that of a tether driven as an antenna are considered. This work was partially supported by the Consiglio Nazionale delle Ricerche under contract No. 81.00952.     

Operation of the EGA electron gun at high gas pressures

Summary This paper presents experimental results on the effects of increasing gas pressure on electron gun operations. The electron gun used is the gun EGA which has been developed for the TSS-1 mission. Various gases have been used with pressures in the range from 10⁻⁶ to a few times 10⁻³ mbar. The measurements, taken in a vacuum chamber, show a steady increase in the slope of theI–V characteristics of the gun when the pressure is increased, as a consequence of ionization phenomena induced by the electron beam. Further measurements have been taken of the overall current on a target at some distance from the gun itself. An attempt is also made at a theoretical calculation of the effects observed, based on simplified models.     

Focusing-defocusing phenomena of radio echo signal after passage of the morning solar terminator

Summary Campaign results of high-repetition ionospheric soundings, performed at the ionospheric station of Rome using a Digisonde 128P, are presented. We introduce an index derived from run rapid ionograms that can be used to detect oscillations of isodensity surfaces ofF ionospheric region started by morning solar terminator.     

Response of auroral regions to directional changes of the interplanetary magnetic field: Case study

Summary On October 6, 1979, the low-altitude polar-orbiting satellites DMSP-F2 and-F4 crossed the auroral electron precipitation region in the opposite hemispheres at nearly the same universal time (UT) and in the same magnetic local-time (MLT) sector near midnight. Three pairs of such nearly simultaneous conjugate crossings took place during a period of enhanced magnetic activity and strongly turning northward or southward of the interplanetary magnetic field (IMF). These conjugate observations allowed the study, with time resolution better than six minutes, of the variation, in response to directional changes of the interplanetary magnetic field, of the latitudinal position and width of the auroral regions; these are believed to map the central plasma sheet (CPS) and boundary plasma sheet (BPS). During the equatorward expansion of the whole auroral electron precipitation region, its latitudinal width is observed to decrease markedly when the IMF turns from a northern to a southern direction. In particular, a different response of the equatorward boundary of the auroral oval with respect to the poleward boundary results from the observations, showing that the speed of the equatorward expansion of the equatorward boundary, measured at a temporal resolution of less than 6 minutes, is lower than the speed of the poleward boundary. The BPS/CPS boundary moves coherently with the southward turning of the IMF, with intermediate speed. It follows that the latitudinal width of the poleward part of the auroral region, assumed to map the boundary plasma sheet, decreases more dramatically than the width of the equatorward part of the region mapping the central plasma sheet. These findings could be explained in terms of changes of the total open magnetic flux. Actually, the equatorward shift of the poleward boundary of the auroral oval and the subsequent dramatic thining of the BPS region seem to be the consequence of a larger number of geomagnetic flux line interconnected with the IMF during a southward IMF condition.     

Langmuir probe measurements in the sheath of a highly charged body

Summary We perform a model study of the electrical characteristics of a Langmuir probe moving in the field of a highly charged central body. The study is mainly motivated by a recent proposal, in the context of the Tethered Satellite System project, where the use of probes to study the space charge region surrounding a highly charged satellite is foreseen.

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Riassunto Si presenta un’analisi delle caratteristiche elettriche di una sonda di Langmuir nel campo elettrico di un corpo centrale ad alto stato di carica. Lo studio è soprattutto motivato da una recente proposta di esperimento per il progetto Tethered Satellite System dove si prevede l’uso di sonde per studiare la regione di carica spaziale attorno da un satellite a elevati potenziali.

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Измерения с помошью Ленгмюровского зонда в оболочке сильно заряженного тела

Резюме Предлагается анализ Электрических характеристик Ленгмюровского зонда, движушегося в поле центрального сильно заряженного тела. Йсследование, в основном, было обусловлено недавно предложенным Экспериментом в связи с проектом ? привязанной спутниковой системы ? в котором предполагается использование зондов для исследования области пространственного заряда, окружаюшей сильно заряженный спутник.

     

Ripple damping on water surface covered by a spreading film: Theory and experiment

Summary The results of point-by-point laboratory dampingvs. frequency measurements using mechanically generated ripples on a water surface covered by monomolecular film of oleic alcohol are discussed in terms of a theory that takes into account coupling of Laplace and Marangoni modes.

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Riassunto Una teoria delle onde gravito-capillari alla superficie di acqua ricoperta da un film monomolecolare di spandimento, che tien conto dei modi di Laplace e di Marangoni, e del loro accoppiamento, è usata per guistificare delle misure di smorzamento ondoso effettuate in vasca con film di alcool oleico.

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Резюме В рамках теории, которая учитывает связь мод Лапласа в Марангони, обсуждаются результаты лабораторных измерений затухания в зависимотси от частоты. При измерения использовалась механически возбужденная рябь на поверхности воды, покрытой мономолекулярной пленкой олеинового спирта.

     

Experimental activity and numerical simulations for the plasma experiment of the ESA CLUSTER Project

Summary The ESA CLUSTER project consists of a cluster of four space-crafts which, when orbiting close to one another, will allow a detailed study of the terrestrial magnetosphere and of its interaction with the solar wind. IFSI actively participates in this project with the conceptual design and mechanics of the hot ion analyser for the Cluster Ion Spectrometer experiment (CIS). This analyzer is of the ?top-hat? type and provides the three-dimensional distribution function of ions in the (0÷40) keV range every two seconds. Within this project, the experimental activity of the group consisted in setting up a vacuum chamber with ion source, mass spectrometer and two azimuthal and polar rotating platforms, in dedicating a computer to data acquisition and monitoring of the physical parameters such as pressure inside the chamber and, finally, in the construction of a prototype of the sensor. The theoretical activity, preliminary to the design of the sensor, is based on the numerical simulation of the sensor in various geometries. It is the aim of the present study to compare between the experimental and theoretical response of the sensor for two different configurations. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.     

Surface circulation in the Northern Adriatic Sea as revealed by a drifter experiment

Summary Nine-hours-averaged positions from five satellite-tracked drifting buoys were used to map the surface circulation in the Northern Adriatic sea. The velocity and kinetic-energy fields were calculated on a regular (0.1×0.1)^o grid using averaged positions and remapping the obtained field by means of univariate objective analysis techniques. Eddy and mean flow kinetic-energy contributions were also calculated on a (0.1×0.1)^o grid. The main features of the surface circulation agree with other representations. The double eddy regime due to the Po river outflow, which spreads in a typical summer regime and the corresponding low-dynamics coastal regime along the Italian littoral south the Po outlet are rather well resolved.     

New remarks on the magnetic-field regime in the distant geomagnetic tail: Pioneer 8

Summary The emerging overview of the distant tail suggests to interpret some aspects of the magnetic-field observations obtained during January 1968 by Pioneer 8 in the region of expected tail (∼500R _E) in terms of different magnetic-field regimes which might find correspondence in the experimental observations performed at ∼240R _E by ISEE-3. At Pioneer position tail-like fields are typically accompanied by significant values of theB _y component while evidence for a wave activity which mostly perturbs the trasversal magnetic-field components is occasionally detected during tail-like encounters. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.