Introduction to SEP effects on spacecraft hardware

The most energetic particle populations found in the heliosphere are the constant flux of Galactic Cosmic Rays (GCRs) and the sporadic SEP events. One of the major sources of radiation damages to spacecrafts is attributed to penetrating high energy solar protons. Radiation effects on electrical and electronic space systems and materials are usually considered in terms of cumulative radiation damages and single event effects (SEE) [1].

Cumulative radiation damage

Cumulative radiation damages can be attributed to both total ionizing (TID) and non-ionizing radiation doses. Radiation dose is the quantity of energy per unit mass transferred by particles at a target material from ionisation and excitation, and it usually refers to the energy absorbed locally per unit mass as a result of radiation exposure. The unit in SI is the gray: 1 Gy = 1 J/kg, but in practice the unit of rad (radiation absorbed dose) is used: 1 rad = 1 cGy.
Total ionizing dose (TID) effects
Materials such as polymers, semiconductors, insulators, and glasses are susceptible to TID effects and can suffer degradation in mechanical, electrical and optical properties. The evaluation of the TID on a component is usually calculated through the "dose profile curve" which indicates the dose received through a shield of varying thickness. The TID that electronic devices can withstand depends on the technology. Typical values for standard CMOS (Complementary Metal-Oxide-Semiconductor) COTS (Commercial-Of-The-Shelf) are in the range of few krad, for CMOS rad hard devices are in the range of 0.1–1 Mrad, for bipolar in the range of 10–100 krad while AsGa can withstand a TID of the order of Mrad [2].
Total non-ionizing dose and displacement effects
Displacement effects are caused by crystal structure damages due to the energy particle loss induced by elastic or inelastic collisions in a material. The displacement effect is quantitatively measured by the Non Ionising Energy Loss (NIEL) coefficient which expresses the rate of energy loss in a material by a particle due to displacement damage per unit path length. The orders of typical values of displacement effects are 1011 n/cm2 for CCD and optolinks, 1011 n/cm2 for bipolar, 1014 n/cm2 for MOS and 1015 n/cm2 for AsGa (1 "n" corresponds to 1 MeV) [2].

Single event effects

Solar energetic particles are also responsible for a number of specific effects caused by direct ionization from single particles traversing through the active volume of an electronic device. The associated "iono-current" can induce several destructive effects—which are grouped under the heading SEE (Single Event Effect)—such as:

SEP effects and SEPEM

The SEPEM application server provides the following utilities for analysis of SEP effects:


[1] N.B. Crosby, Universal Heliophysical Processes, Proc. IAU Symposium 257, 47 (2008).
[3] Jean-Claude Boudenot, in R. Velazco et al. (eds.), Radiation Effects on Embedded Systems, Springer. p. 1-9 (2007).

Last modified: 19.05.2010 by IS