NASA Scientific and Technical Aerospace Reports

This paper presents a dynamic technique for predicting the effect that a ‘location’ of a program will have on the program’s
computational behavior. The technique is based on the three necessary and sufficient conditions for software failure to occur:
(1) a fault must be executed, (2) the fault must adversely affect the data state, and (3) the adverse effect in a data state must
affect program output. In order to predict the effect that a location of a program will have on the program’s computational
behavior, the following characteristics of each program location are estimated: (1) the probability that a location of the
program is executed, (2) the probability that a location of the program noticeably affects the program state created by the
location, and (3) the probability that the data states created by a location affect the program’s output. With estimates of these
characteristics for each location in a program, we can predict those locations where a fault can more easily remain undetected
during testing, as well as predict the degree of testing necessary to be convinced that a fault is not remaining undetected in
a particular location.
Author
Computer Systems Programs; Mathematical Models; Software Reliability; Performance Tests; System Failures; Dynamic
Models
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CYBERNETICS, ARTIFICIAL INTELLIGENCE AND ROBOTICS
Includes feedback and control theory, information theory, machine learning, and expert systems. For related information see also 54
Man/System Technology and Life Support.
20040111074 Alcatel Space Industries, Cannes la Bocca, France
SPARCS: An Advanced Software for Spacecraft Charging Analyses
Clerc, S.; Brosse, S.; Chane-Yook, M.; 8th Spacecraft Charging Technology Conference; March 2004; 7 pp.; In English; See
also 20040111031; No Copyright; Avail: CASI; A02, Hardcopy
We report on the development of SPARCS (SPAcecRaft Charging Software), a simulation tool for spacecraft charging
analyses. The code computes electron and ion currents from the magnetosphere on the surfaces of the satellite with a
back-trajectories algorithm. Secondary emission and photo-emission currents are computed using standard models. Special
care is given to the computation of recollected secondary electrons. The current balance is used to update the absolute and
differential potentials. The code also computes the potential around the spacecraft, which is in turn used to compute electrons
and ions collection. In a geostationary environment, space charge can be neglected. The resulting Poisson equation is solved
with a Finite Element method on an unstructured mesh, coupled with Infinite Elements to enforce the correct decay of the
potential at infinity. Large time steps can be used thanks to a quasi-implicit method. We describe our validation strategy and
give some preliminary results of this work program. Finally, optimization of the linear system solver with the HYPRE library
and parallelization keep the run time low, making SPARCS a fast and accurate tool for spacecraft charging analyses.
Author
Computerized Simulation; Spacecraft Charging; Computer Programs; Mathematical Models; Electrostatic Charge
20040111095 Swedish Inst. of Space Physics, Kiruna, Sweden
Feedback on the PicUp3D Experience and the Open Source Strategy Applied to a Spacecraft-Plasma Interaction
Simulation Code
Forest, Julien; Hilgers, Alain; 8th Spacecraft Charging Technology Conference; March 2004; 10 pp.; In English; See also
20040111031
Contract(s)/Grant(s): ESA-13590/99/NL/MV; No Copyright; Avail: CASI; A02, Hardcopy
PicUp3D is an electrostatic multi-species 3D Particle-In-Cell (PIC) code dedicated to the modeling of the electrostatic
sheath of spacecraft. Fully written in JAVA and able to model 3D realistic geometries, PicUp3D is designed to perform fine
modeling for various purposes, especially scientific instruments calibration, and active device environment analysis such as
ion thrusters. The development of PicUp3D was initiated in the context of the IPICSS project, for Investigation of Plasma
Induced Charging of Satellite Systems, in partnership between IRF-K, ESA, CNRS/CETP and CNES, in the framework of the
SPINE network and an ESA Academic Research Programme. The development time was followed by a long validation phase
during which PicUp3D was intensively tested and used for mission supports at ESA. These application cases have confirmed
the ability of PicUp3D models to simulate correctly modern spacecraft-plasma interactions problems. To induce a strong
synergy with the scientific and the industrial communities, PicUp3D was developed with an open source software approach,
such that the source code is freely accessible and the models can be tailored, validated or deeply modified by advanced users.
PicUp3D has been released (http://www.spis.org) for the first time in December 2002 under the GPL license and is now freely
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