Browsing by Author "Gingras, Benjamin"
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Item The International Space Station Space Radiation Environment: Avionics systems performance in low-Earth orbit Single Event Effects (SEE) environments(48th International Conference on Environmental Systems, 2018-07-08) Koontz, Steve; Suggs, Robert; Alred, John; Worthy, Erica; Steagall, Courtney; Hartman, William; Gingras, Benjamin; Schmidl, William; Boeder, PaulSingle 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.Item International Space Station Spacecraft Charging Environments: Modeling, Measurement, and Implications for Future Human Space Flight Programs(48th International Conference on Environmental Systems, 2018-07-08) Koontz, Steven; Suggs, Robert; Alred, John; Worthy, Erica; Hartman, William; Gingras, Benjamin; Schmidl, WilliamSpacecraft charging analysis and mitigation is an interdisciplinary subject combining aspects of electrostatics, plasma physics, ionizing radiation, and materials science, as well as electronic systems electromagnetic interference and compatibility (EMI/EMC) effects. Spacecraft charging hazards are caused by the accumulation of electrical charge on spacecraft and spacecraft components produced by interactions with space plasmas, energetic charged particles, and solar UV photons as well as spacecraft electrical power and propulsion systems operations. Spacecraft charging hazard effects include both hard and soft avionics and electrical power system anomalies and have led to the partial or complete loss of numerous spacecraft. The International Space Station (ISS) orbital altitude and inclination (~400 km and 51.6 degrees) determines the dominant natural environment factors affecting ISS spacecraft charging: 1) high speed flight through the geomagnetic field and 2) electrical power system interaction with the cold, high-density ionospheric plasma. In addition ISS is exposed to energetic auroral electrons at high latitude. In this paper we compare ISS spacecraft charging measurements with numerical modeling of ISS charging processes. ISS is a large metallic structure and flight through the geomagnetic field at orbital speed dominates ISS charging. Collection of ionospheric electrons by the large 160 V photo-voltaic arrays is the next largest contributor. Charging by auroral electrons is detectable but makes a relatively minor contribution. Finally, we report the observation of short duration (~ 1 sec) rapid charging peaks associated with shunt/un-shunt operations of the 160 V photo-voltaic arrays, a phenomena not predicted before flight. ISS spacecraft charging environments are radically different from those encountered at higher altitudes in Earth’s magnetosphere, and in cis-Lunar space. We present a brief review of those charging environments and an assessment of the applicability of ISS spacecraft charging management and flight experience to future human spaceflight programs beyond LEO.