Electrodynamic deorbiting of LEO satellites

In this paper we present realistic calculations of deorbiting times for a LEO satellite through the use of electrodynamic tethers. We refer to two possible tether systems (a bare and a conducting insulated tether) both equipped with an inflatable conducting balloon at the upper end. The calculations take into account average ionospheric properties and the electrical interaction of the wire with the ionosphere. Furthermore, they have been done for several inclination orbits and include also the deviation of the tether from the vertical direction under the combined action of the gravity gradient and the electrodynamic forces. The results obtained for the decay times, for typical constellation satellite, indicate that such tether systems are definitely of interest for the deorbiting application

Electron collection by a charged satellite in the ionospheric plasma

The space charge region surrounding a highly charged, electron collecting, spacecraft moving in the ionospheric plasma, can be divided into an inner zone (close to the spacecraft), where electron collection is isotropic with respect to the magnetic-field direction, and an outer zone where the electrons are mainly collected along magnetic field lines. In this paper we outline a theory to obtain the current voltage characteristic of such a positive satellite. It is shown that the theoretical results compare very favorably with the experimental data obtained by the TSS-1R mission

Current collection by a highly positive body moving in the ionospheric plasma

In this paper we derive an interesting feature of the space charge region surrounding a positively charged body moving in a magnetoplasma and, precisely, the fact that, for potentials of the body in excess of a certain value, at least in an inner region close to the body, the electron collection (and the structure of the self-consistent potential) is isotropic. This is used to derive current-voltage characteristics for such a situation. These theoretical characteristics are then convincingly compared with those obtained from the analysis of the data obtained during the recently flown TSS-1R mission

The TSS-1 mission: Results on satellite charging

In the present paper we first give a short account of the mission TSS-1 flown on the Shuttle sts-46 in August 1992 and its basic electrical configurations. We then show some results obtained from the experiment RETE on board the satellite which are relevant for the issue of satellite charging

Laboratory simulation of the electrodynamic interactions of a tethered satellite with an ionospheric plasma

An improved experimental set-up in the Orleans Plasma Chamber allowed investigations of the I-V characteristics of a conductive spherical body (10 cm diameter) in a plasma environment. Moreover, the influence of a transversal magnetic field at 0.6 and 1.2 G was investigated, for the first time, both on the sheath potential profile and current collection. Floating potential profiles were measured at 16 different radial distances from the test body up to 9 body radii in 8 different angular positions. The test body potential could be increased in the range from -200 V up to +100 V. Preliminary results are shown and discussed

Electromagnetic propagation features of ground-penetrating radars for the exploration of Martian subsurface

In this work, the effects of magnetic inclusions in a Mars-like soil are considered with reference to the electromagnetic propagation features of ground-penetrating radars (GPRs). Low-frequency and time-domain techniques, using L-C-R meters and TDR instruments, respectively, are implemented in laboratory experimental set-ups in order to evaluate complex permittivity and permeability and wave velocity for different scenarios of a dielectric background medium (silica) with magnetic inclusions (magnetite). Attenuation and maximum detection ranges have also been evaluated by taking into account a realistic GPR environment, which includes the transmitting/receiving antenna performance and the complex structure of the subsurface. The analysis and the interpretation of these results shed new light on the significant influence of magnetic inclusions on the performance of Martian orbiting and rover-driven GPRs.Published5-11reserve

Current collection to long conductors with wide geometries for bare electrodynamic tether applications - A laboratory update

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77101/1/AIAA-2002-1123-228.pd

Triple Probe System For In Situ Ionospheric Plasma Monitoring

The capability to establish the magnitudo, time and place of a forthcoming earthquake is still far from having a reliable and accurate prevision of practical interest. Different precursory phenomena of forthcoming earthquakes have been experimentally observed; they are mostly linked to a microfracturation of the rock due to stress accumulation during the pre-seismic phase in the hypocentral zone of an earthquake. The microcracks in the rocks can be considered seismic sources able to generate electromagnetic emissions, in particular in ULF-ELF bands (0-3000 Hz). The electromagnetic waves spread through the lithosphere to the ionosphere and the magnetosphere and they produce irregularities (Earth magnetic field variations, ionospheric plasma parameters disturbances and particles precipitation from Van Allen belts). In addition, the shallow earthquakes are capable to produce gravity oscillations, propagating upwards and coupling with neutral atmosphere and, eventually, with ionospheric layers. Significant variations of the total electron content in the ionosphere have been measured through GPS receivers. A space mission seems to be an affordable way to achieve in-situ observations, overall the Earth. A plasma diagnostic system suitable to be hosted on board LEO satellites to investigate the presence of ionosphere disturbances has been designed, manufactured and tested. The system is an electrostatic probe, specifically a Triple Probe System (TPS), which allows the local plasma density and electron temperature determination through acquisition of instantaneous voltage and current measurements. A prototype has been arranged to be hosted on board UNISAT-4, a low-cost university satellite built by GAUSS (Gruppo di Astrodinamica \u2013 Universit\ue0 degli Studi di Roma \u201cLa Sapienza\u201d), scheduled to be launched on December 2005. The paper deals with the TPS basic concepts and some preliminary results, obtained in a test campaign carried out in a climatic room from -40\ub0C to +60\ub0C, are depicted