2015.B.3.5. SurfSat – Surface charging and ESD measurements on a CubeSat
Adrienne Dove (1)
Joshua Colwell (1)
Janessa Buhler (1)
- University of Central Florida, United States of America
plasma, surface charging, ESD
Spacecraft in low-Earth orbits experience a wide range of charging conditions as they pass through the ambient atmospheric and plasma environments. We are designing a CubeSat, called SurfSat, which will take in-situ measurements of the charging of spacecraft materials in the context of the surrounding plasma environment. Charging issues occur on spacecraft in both Geosynchronous and Polar orbits due to the ambient plasma environment. The space radiation environment in Earth’s atmosphere is filled with hot and low-density plasmas that can cause charge to build up on spacecraft surfaces, resulting in high differential voltages and subsequent electrostatic discharges. If the exposed spacecraft materials are not properly bonded, differential charging can occur which can result in unwanted and damaging electrostatic discharge (ESD) events. These discharges can damage avionics and/or scientific instruments on spacecraft. While mitigation of surface charging can be relatively straightforward to achieve, many spacecraft materials cannot meet the resistivity requirements due to higher priority optical or thermal constraints.
SurfSat will use a Langmuir probe system to measure the ambient plasma environment, take in-situ measurements of the ground current waveforms from chosen common spacecraft dielectric material samples, and measure the spacecraft and material potentials. The sample materials will span a range of resistivities that will be chosen both for relevance and in order to maximize scientific return. Understanding the charging behavior requires a full assessment of the environment as well as the effects of electrostatic discharges from the culprit materials on sensitive components. The energy from ESD events can couple through direct current injection, or the radiated emissions from the event can couple both capacitively and inductively. Knowledge of the ESD arc’s current waveform is required in order to assess a circuit’s susceptibility without performing a potentially damaging ESD test. Comparison of on-orbit ESD measurements with completed and ongoing plasma chamber charging experiments will be used to validate current plasma charging test methods. These experiments will be used to develop design criteria, and help avoid potentially disastrous discharging on spacecraft. Additionally, if the spacecraft orbit is high-inclination, these in situ measurements could be used in conjunction with existing Kp index prediction tools to determine viability in using magnetic indexing as a launch constraint for preventing undesired surface charging on launch vehicle materials.
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