This paper re-examines the use of the SEU Figure of Merit for heavy ion ups
et rate predictions Slightly different orbit dependent rate coefficients ar
e used for unhardened and hardened parts. The two different coefficients al
low for the slight changes of LET spectra that occur due to the earth's mag
netic shielding. Accurate heavy ion predictions can be made for any orbit a
nd any part.
We show that the Figure of Merit can also be used to predict upset rate due
to protons in the proton radiation belt. A proton rate coefficient is intr
oduced to describe the upset likelihood in orbits with proton exposures. Th
ese results mean that a part susceptibility can be described by a single pa
rameter, rather than the four Weibull parameters and two Bendel parameters
used previously. The Figure of Merit completely describes a part's SEU susc
eptibility and can be obtained from either proton or heavy ion measurements
, eliminating the expense of making both types of experiment.
The total upset rate for a part in a particular orbit can be calculated usi
ng its characteristic Figure of Merit and a single orbit specific rate coef
ficient, the sum of the heavy ion and proton rate coefficients.