The International Space Station Space Radiation Environment: Avionics systems performance in low-Earth orbit Single Event Effects (SEE) environments

Single event effects (SEE) are those errors, anomalies, or failures in microelectronic devices caused by the passage of a single energetic charged particle through the device. Spacecraft SEE environments consist primarily of energetic charged particles; both primary particles originating in the natural environment and secondary particles (including secondary neutrons) produced by nuclear reactions of primary particles with spacecraft materials. The energetic charged particle components (electrons, protons, and atomic nuclei) of the spacecraft SEE environment include galactic cosmic rays (GCR), and planetary radiation belt charged particles, as well as solar energetic particle event (SPE) charged particles.
The International Space Station (ISS) orbital altitude and inclination (~350 km to ~420 km at 51.6 degrees inclination) results in a spacecraft SEE environment that varies dramatically with location in Earth’s geomagnetic field. Geomagnetic GCR shielding diminishes with distance from the geomagnetic equator. Near + 51.6 degrees latitude the ISS GCR environment has a high degree of similarity to the interplanetary GCR environment in cis-Lunar space. SEE environments supporting ISS avionics systems design, development, test, and verification are documented in SSP-30512, Space Station Ionizing Radiation Design Environment. Comparisons of overall ISS avionics systems in-flight performance with pre-flight verification report predictions have been previously reported and meet or exceed expectations in all cases. In this paper we report the results of more detailed investigations of the effects of geographic location, altitude, solar cycle, and spacecraft shielding mass effects on the in-flight SEE performance of the ISS command and data handling system during the past 17 years. In addition, we report on the pre-flight testing and in-flight performance of the commercial-off-the-shelf lap top computers used on ISS. Finally, we present an assessment of ISS as an avionics SEE test and flight demonstration platform for exploration hardware destined for the cis-lunar space.