scope:

Practice:

Operational spacecraft can experience adverse effects from impinging high energy radiation. A single event upset (SEU) occurs when a single particle, usually a heavy ion or proton, deposits enough charge at a sensitive node in a microcircuit to cause that circuit to change state. In general, these effects are temporary and appear as "soft failures" such as anomalous bit flips or spurious commands. In extreme cases, latch-up can occur and result in the destructive failure of the part.

The practice is to formulate an energetic particle environment model for calculating single event effect rates by utilizing the JPL statistical models for solar proton, alpha particle and heavy ion fluence. This predicted rate, which is a function of cumulative probability, is a useful measure when specifying shielding thickness to protect susceptible components, employing mitigating software, or both to reduce the risk to an acceptable level. Note that this assessment does not consider concentration of particle radiation due to the Earth's magnetic field, (ref. 1), and factors which are not influenced by shielding thickness, such as GCR (Galactic Cosmic Rays).