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  • 1
    Electronic Resource
    Electronic Resource
    A novel medium-energy ion emitter for active spacecraft potential control (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 2293-2297 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An ion emission instrument has been developed to actively control the electrostatic surface potential of a spacecraft in orbit. Spacecraft surfaces tend to charge positive when their conductive surfaces are partially sunlit, and photoelectrons emitted, and the spacecraft is positioned outside of the very dense plasma region which is referred to as plasmasphere. A small, lightweight instrument with a lifetime of more than 104 h at a nominal emission current of 10 μA was the design goal. The ion emitter is based on the liquid metal ion source principle; a constant stream of liquified indium is evaporated from the tip of a needle and ionized; the ions are then extracted by a strong electric field. The size of the instrument is about 18 by 15 by 23 cm (length×width×height) and the entire instrument weighs about 1.9 kg and consumes 2.4 W of electrical power in the nominal emission mode. An instrument of this type is already operational on the Japanese Geotail spacecraft, while five more instruments are at the stage of flight model assembly for integration on the Russian Interball satellite and the ESA/NASA four-spacecraft Cluster mission. The Geotail instrument is functioning as expected. Preliminary results show that the ion emitter is able to reduce surface potentials of +70 V (highest value observed up to now) down to 2–4 V.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143924
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Energetic ion emission for active spacecraft control
    Amsterdam : Elsevier
    Advances in Space Research 12 (1992), S. 61-64 
    Details
    ISSN: 0273-1177
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0273-1177(92)90353-Y
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Spacecraft potential control aboard Equator-S as a test for Cluster-II (1999)
    Springer
    Annales geophysicae 17 (1999), S. 1582-1591 
    Details
    ISSN: 0992-7689
    Keywords: Space plasma physics (active perturbation experiments ; spacecraft sheaths ; wakes ; charging ; instruments and techniques)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The payload of Equator-S was complemented by the potential control device (PCD) to stabilise the electric potential of the spacecraft with respect to the ambient plasma. Low potentials are essential for accurate measurements of the thermal plasma. The design of PCD is inherited from instruments for Geotail and Cluster and utilises liquid metal ion sources generating a beam of indium ions at several keV. The set-up of the instrument and its interaction with the plasma instruments on board is presented. When the instrument was switched on during commissioning, unexpectedly high ignition and operating voltages of some ion emitters were observed. An extensive investigation was initiated and the results, which lead to an improved design for Cluster-II, are summarised. The cause of the abnormal behaviour could be linked to surface contamination of some emitters, which will be monitored and cured by on-board procedures in future. The mission operations on Equator-S were not at all affected, because of the high redundancy built into the instrument so that a sufficient number of perfectly operating emitters were available and were turned on routinely throughout the mission. Observations of the effect of spacecraft potential control on the plasma remained limited to just one event on January 8, 1998, which is analysed in detail. It is concluded that the ion beam lead to the predicted improvement of the particle measurements even outside the low density regions of the magnetosphere where the effect of spacecraft potential control would have been much more pronounced, and that the similar instruments for the four Cluster-II spacecraft to be launched in 2000 will be very important to ensure accurate plasma data from this mission.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-999-1582-3
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  • 4
    Electronic Resource
    Electronic Resource
    PEACE: A PLASMA ELECTRON AND CURRENT EXPERIMENT (1997)
    Springer
    Space science reviews 79 (1997), S. 351-398 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An electron analyser to measure the three-dimensional velocity distribution of electrons in the energy range from 0.59 eV to 26.4 keV on the four spacecraft of the Cluster mission is described. The instrument consists of two sensors with hemispherical electrostatic energy analysers with a position-sensitive microchannel plate detectors placed to view radially on opposite sides of the spacecraft. The intrinsic energy resolutions of the two sensors are 12.7% and 16.5% full width at half maximum. Their angular resolutions are 2.8° and 5.3° respectively in an azimuthal direction and 15° in a polar direction. The two sensors will normally measure in different overlapping energy ranges and will scan the distribution in half a spacecraft rotation or 2 s in the overlapped range. While this is the fastest time resolution for complete distributions, partial distributions can be recorded in as little as 62.5 ms and angular distributions at a fixed energy in 7.8 ms. The dynamic range of the instrument is sufficient to provide accurate measurements of the main known populations from the tail lobe to the plasmasheet and the solar wind. While the basic structure of the instrument is conventional, special attention has been paid in the design to improving the precision of the instrument so that a relative accuracy of the order of 1% could be attained in flight in order to measure the gradients between the four spacecraft accurately; to decreasing the minimum energy covered by this technique from 10 eV down to 1 eV; and to providing good three dimensional distributions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004938001388
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  • 5
    Electronic Resource
    Electronic Resource
    ACTIVE SPACECRAFT POTENTIAL CONTROL (1997)
    Springer
    Space science reviews 79 (1997), S. 271-302 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Charging of the outer surface or of the entire structure of a spacecraft in orbit can have a severe impact on the scientific output of the instruments. Typical floating potentials for magnetospheric satellites (from +1 to several tens of volts in sunlight) make it practically impossible to measure the cold (several eV) component of the ambient plasma. Effects of spacecraft charging are reduced by an entirely conductive surface of the spacecraft and by active charge neutralisation, which in the case of Cluster only deals with a positive potential. The Cluster spacecraft are instrumented with ion emitters of the liquid-metal ion-source type, which will produce indium ions at 5 to 8 keV energy. The operating principle is field evaporation of indium in the apex field of a needle. The advantages are low power consumption, compactness and high mass efficiency. The ion current will be adjusted in a feedback loop with instruments measuring the spacecraft potential (EFW and PEACE). A stand-alone mode is also foreseen as a back-up. The design and principles of the operation of the active spacecraft potential control instrument (ASPOC) are presented in detail. Flight experience with a similar instrument on the Geotail spacecraft is outlined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004921614592
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    Paper (German National Licenses)
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