Spacecraft Charging and Mitigation

Abstract

Satellites and spacecraft materials can become charged to tens or even thousands of volts when ions in the space environment collide with spacecraft. This can sometimes cause electrical discharge of differentially or internally charged spacecraft materials, which can adversely affect satellite operations. Additionally, high-energy ions can penetrate spacecraft materials and deposit their energy within sensitive electronics, causing component damage or failure. To consider various approaches for spacecraft charge mitigation, 150 technologists from around the world representing government, academia, and industry met at the 11th Spacecraft Charging Technology Conference (SCTC) in Albuquerque, N. M., on 20–24 September 2010 (see Figure 1). The conference was held against the backdrop of the apparent charging event of the Galaxy 15 satellite, which some speculate triggered this geosynchronous communications satellite to cease operations, thereby adversely affecting related satellite-reliant communities (see J. Allen, Space Weather, 8, S06008, doi:10.1029/2010SW000588, 2010). Charles P. Pike, formerly of the U.S. Air Force Research Laboratory (AFRL) and past program manager of the AFRL spacecraft charging program, presented a keynote address that recalled the early 1970s, when military satellites in geosynchronous orbit experienced numerous unexpected performance anomalies. Pike then traced how scientists discovered that space weather can have deleterious and sometimes catastrophic effects on spacecraft, satellite operations, and the longevity of space systems. Speakers focused on the ways that energetic charged particles and plasma can adversely affect spacecraft. For example, electrostatic discharge (ESD) of solar cell arrays, on which most spacecraft depend, can destroy the supply of energy to crucial satellite systems. As spacecraft power requirements grow, the current trend toward higher solar panel operating voltages (above 100 volts) increases the environmental susceptibility of spacecraft. Presentations featured ESD mitigation strategies designed and analyzed by researchers from institutions within the United States, Japan, and Europe. Much of the conference focused on the ESD of satellites in geosynchronous orbit, although consideration was also given to other Earth orbits as well as other planetary missions and solar probes. Also discussed were laboratory testing approaches for simulating spacecraft-environment interactions and computer modeling of complex satellite geometries. Many talks at the conference showed how researchers are advancing the science and capabilities of tools, models, material properties, guidelines, and best practices to build robust satellites equipped with spacecraft charging mitigation capabilities. Further, various engineering standards for environmentally tolerant space systems, including those available from NASA (NASA-HDBK-4002A), the International Organization for Standardization (ISO/DIS 11221), and the European Space Agency (ECSS-E-ST-10-04C), are proving useful, meeting participants agreed. Attendees also discussed new technology frontiers for addressing spacecraft charging, which they agreed should focus on better specifications for nonstatic spacecraft materials, advancement of dynamic models of spacecraft-environment interactions, development of novel techniques for spacecraft charge mitigation, and assessing the impacts of new requirements for high-voltage solar panels. Presentations and proceedings of this meeting are available through the National Geophysical Data Center (http://www.ngdc.noaa.gov/stp/satellite/anomaly/2010_sctc/). In addition, a special issue of IEEE Transactions on Plasma Science will be devoted to follow-on and related papers covering spacecraft charging issues. The 12th SCTC is planned for Kitakyushu, Japan, in May 2012. Dale Ferguson is a physicist with the Battlespace Environment Division at AFRL in Albuquerque, N. M. David Cooke is the technical advisor for the AFRL Space Weather Center of Excellence at Hanscom Air Force Base in Bedford, Mass. William Denig is chief of the Solar and Terrestrial Physics Division at NOAA's National Geophysical Data Center in Boulder, Colo. E-mail: william.denig@noaa.gov.