NASA Scientific and Technical Aerospace Reports

20040111068 European Space Agency. European Space Research and Technology Center, ESTEC, Noordwijk, Netherlands
European Approach to Material Characterization for Plasma Interaction Analysis
VanEesbeek, Marc; Hilgers, Alain; Reulet, Rene; Dirassen, Bernard; Levy, Leon; Montero, Isabel; Galan, Luis; 8th Spacecraft
Charging Technology Conference; March 2004; 10 pp.; In English; See also 20040111031; No Copyright; Avail: CASI; A02,
Hardcopy
The European Space Agency (ESA) has initiated an activity on material characterisation for plasma interaction analysis.
This work is part of a mini-project in the frame of the ESA Technology Research Program, which is also covering two other
main aspects of the research and industry community needs, i.e. (1) Spacecraft plasma interaction analysis and simulation
software toolkit and (2) Guidelines for spacecraft charging and plasma interactions. The activities in the three parts will be
harmonized in the framework of SPINE (Spacecraft Plasma Interaction Network in Europe). The main objectives of the
activities described in this paper are: (1) Definition of required material characteristics needed for the different simulation
software, the comparison of different characterisation techniques and the available test houses in Europe. (2) Design of a
database for relevant properties on materials used in spacecraft manufacturing; largely concentrated on external surfaces. (3)
Collection and integration of existing, and verifiable, material property data into an easy accessible database, compatible with
the software under development. (4) Measurement of properties on a set of newly proposed materials.
Author
Plasma Interactions; Computer Programming; Computerized Simulation; Software Development Tools; Spacecraft Charging
20040111083 NASA Johnson Space Center, Houston, TX, USA
Specification of ISS Plasma Environment Variability
Minow, Joseph I.; Neergaard, Linda F.; Bui, Them H.; Mikatarian, Ronald R.; Barsamian, H.; Koontz, Steven L.; 8th
Spacecraft Charging Technology Conference; March 2004; 15 pp.; In English; See also 20040111031
Contract(s)/Grant(s): NAS8-00187; No Copyright; Avail: CASI; A03, Hardcopy
Quantifying spacecraft charging risks and associated hazards for the International Space Station (ISS) requires a plasma
environment specification for the natural variability of ionospheric temperature (Te) and density (Ne). Empirical ionospheric
specification and forecast models such as the International Reference Ionosphere (IRI) model typically only provide long term
(seasonal) mean Te and Ne values for the low Earth orbit environment. This paper describes a statistical analysis of historical
ionospheric low Earth orbit plasma measurements from the AE-C, AE-D, and DE-2 satellites used to derive a model of
deviations of observed data values from IRI-2001 estimates of Ne, Te parameters for each data point to provide a statistical
basis for modeling the deviations of the plasma environment from the IRI model output. Application of the deviation model
with the IRI-2001 output yields a method for estimating extreme environments for the ISS spacecraft charging analysis.
Author
Atmospheric Density; Atmospheric Models; Environment Models; Forecasting; Hazards; Spacecraft Charging; Statistical
Analysis
20040111092 NASA Glenn Research Center, Cleveland, OH, USA
Solar Array in Simulated LEO Plasma Environment
Vayner, Boris; Galofaro, Joel; Ferguson, Dale; 8th Spacecraft Charging Technology Conference; March 2004; 16 pp.; In
English; See also 20040111031; No Copyright; Avail: CASI; A03, Hardcopy
Six different types of solar arrays have been tested in large vacuum chambers. The low Earth orbit plasma environment
was simulated in plasma vacuum chambers, where the parameters could be controlled precisely. Diagnostic equipment
included spherical Langmuir probes, mass spectrometer, low-noise CCD camera with optical spectrometer, video camera, very
sensitive current probe to measure arc current, and a voltage probe to register variations in a conductor potential. All data
(except video) were obtained in digital form that allowed us to study the correlation between external parameters (plasma
density, additional capacitance, bias voltage, etc) and arc characteristics (arc rate, arc current pulse width and amplitude, gas
species partial pressures, and intensities of spectral lines). Arc inception voltages, arc rates, and current collections are
measured for samples with different coverglass materials and thickness, interconnect designs, and cell sizes. It is shown that
the array with wrapthrough interconnects have the highest arc threshold and the lowest current collection. Coverglass design
with overhang results in decrease of current collection and increase of arc threshold. Doubling coverglass thickness causes the
increase in arc inception voltage. Both arc inception voltage and current collection increase significantly with increasing a
sample temperature to 80 C. Sustained discharges are initiated between adjacent cells with potential differences of 40 V for
the sample with 300 m coverglass thickness and 60 V for the sample with 150 m coverglass thickness. Installation of cryogenic
pump in large vacuum chamber provided the possibility of considerable outgassing of array surfaces which resulted in
significant decrease of arc rate. Arc sites were determined by employing a video-camera, and it is shown that the most probable
296