NASA Scientific and Technical Aerospace Reports

20040111090 National Oceanic and Atmospheric Administration, Boulder, CO, USA
Operational Prediction and Specification of the Spacecraft Charging Environment
Onsager, Terrance; 8th Spacecraft Charging Technology Conference; March 2004; 17 pp.; In English; See also 20040111031;
No Copyright; Avail: CASI; A03, Hardcopy
Fluxes of outer radiation belt electrons change dramatically over a broad range of time scales, ultimately driven by the
solar wind, but controlled within the magnetosphere by the action of numerous acceleration and loss mechanisms. The particle
dynamics are influenced by both adiabatic and non-adiabatic processes, involving in-situ acceleration or loss as well as
diffusion either into or out of the radiation belt across its inner and outer boundaries. (see recent review by Friedel et al.
[2002]). Although many different processes have been shown to cause either acceleration or loss of radiation belt particles
under different circumstances, there currently is not a quantitative understanding of which processes dominate under any
specific conditions. Without this quantitative understanding of the competing source and loss mechanisms, accurate
physics-based modeling of the time-dependent radiation belts is not possible.
Derived from text
Outer Radiation Belt; Solar Wind; Spacecraft Charging
20040111238 NASA Langley Research Center, Hampton, VA, USA
Effects of Target Fragmentation on Evaluation of LET Spectra From Space Radiation in Low-Earth Orbit (LEO)
Environment: Impact on SEU Predictions
Shinn, J. L.; Cucinotta, F. A.; Badhwar, G. D.; ONeill, P. M.; Badavi, F. F.; [1995]; 9 pp.; In English; No Copyright; Avail:
CASI; A02, Hardcopy
Recent improvements in the radiation transport code HZETRN/BRYNTRN and galactic cosmic ray environmental model
have provided an opportunity to investigate the effects of target fragmentation on estimates of single event upset (SEU) rates
for spacecraft memory devices. Since target fragments are mostly of very low energy, an SEU prediction model has been
derived in terms of particle energy rather than linear energy transfer (LET) to account for nonlinear relationship between range
and energy. Predictions are made for SEU rates observed on two Shuttle flights, each at low and high inclination orbit.
Corrections due to track structure effects are made for both high energy ions with track structure larger than device sensitive
volume and for low energy ions with dense track where charge recombination is important. Results indicate contributions from
target fragments are relatively important at large shield depths (or any thick structure material) and at low inclination orbit.
Consequently, a more consistent set of predictions for upset rates observed in these two flights is reached when compared to
an earlier analysis with CREME model. It is also observed that the errors produced by assuming linear relationship in range
and energy in the earlier analysis have fortuitously canceled out the errors for not considering target fragmentation and track
structure effects.
Author
Environment Models; Evaluation; Particle Energy; Linear Energy Transfer (Let); Galactic Cosmic Rays; Single Event Upsets
20040112025 NASA Glenn Research Center, Cleveland, OH, USA
Solar Array Arcing in LEO How Much Charge is Discharged?
Ferguson, D. C.; Vayner, B. V.; Galofaro, J. T.; [2004]; 8 pp.; In English; ICPMSE-7, 10-13 May 2004, Toronto, Canada
Contract(s)/Grant(s): 319-20-D1; No Copyright; Avail: CASI; A02, Hardcopy
It is often said that only the solar array or spacecraft surface that can be reached by an arc plume are discharged in a solar
array arc in LEO (Low Earth Orbit). We present definitive results from ground test experiments done in the National Plasma
Interactions (N-PI) facility at the NASA Glenn Research Center that this idea is mistaken. All structure surfaces in contact with
the surrounding plasma and connected to spacecraft ground are discharged, whether the arc plasma can reach them or not.
Implications from the strength and damaging effects of areas on LEO spacecraft are discussed, and mitigation techniques are
proposed.
Author
Solar Arrays; Plasmas (Physics); Plasma Interactions
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