Geosynchronous orbit (GEO) weathering induces differential charging of spacecraft surfaces due to simultaneous fluxes of electrons with a wide distribution of energies onto, into, and through spacecraft surface materials. Thus, satellite surfaces can charge thousands of volts with respect to each other whereas entire satellites can charge tens of thousands of volts negative of their surrounding space plasma. The ensuing electric fields can cause local discharges (arcs) from one part of the spacecraft to another, endangering the normal operation of the satellite. Arcing on solar panels can cause reduced optical transmission through solar cell coverglasses which will lead to reduced power production negatively affecting a long-term satellite missions. This work focuses on evaluation of simulated GEO space weather effect, comprised by < 90 keV high-energy electron irradiation, on optical and charge transport properties of two different types of commonly used space solar cells coverglasses, CMX and CMG.
KEYWORDS: Satellites, Solar energy, Global Positioning System, Solar radiation, Solar cells, Electrons, Contamination, Telescopes, Space operations, Silica
The harsh space environment at geosynchronous orbit (GEO) induces differential charging of spacecraft surfaces due to fluxes of high energy electrons onto and through them. Thus, satellite surfaces can charge thousands of volts with respect to each other whereas entire satellites can charge tens of thousands of volts negative of their surrounding space plasma. The ensuing electric fields can cause local discharges (arcs), endangering the normal operation of the satellite. Solar cell coverglass contamination induced by the high rate of arcing is sufficient to produce the ~1.5 percent/ year power loss in excess of radiation damage on the global positioning system (GPS) satellites. This work focuses on evaluation of a GEO space weather effect, caused by 90 keV high-energy electron radiation, on material properties of different types of commonly used in space solar cell coverglasses (CMX, fused silica, and 0214). Charge analysis performed with a GPS Block IIF NASCAP model demonstrated that the use of CMX, a high-conductivity coverglass, may help to mitigate differential charging and prevent arc-induced contamination. Finally, radiofrequency observations by the Arecibo 305 m telescope of GEO satellites with different configurations have registered abundant arcing of satellites utilizing less conductive coverglasses and no arcing on two with CMX coverglasses. It is the object of the current study to see how space weathering of different coverglass types may alter these results.
Ground- and space-based optical observations of space objects rely on knowledge concerning how spacecraft materials interact with light. One common surface material for many currently active spacecraft is Kapton-HN polyimide. Changes in optical signature for polymeric materials can occur due to surface degradation, leading to altered reflectivity, or due to radiation induced chemical modification, leading to an alteration of a material’s absorption/transmission properties. The optical fingerprints of commonly used materials change continuously under exposure to high energy electrons, a primary damaging species in geostationary Earth orbit (GEO). Laboratory observations show that these changes in a material’s optical signature are wavelength dependent and to some degree transient. This work investigates the changes in the optical reflection behavior of a variety of aerospace materials before and after electron irradiation. The results of this investigation will find use in the space debris remediation community for characterization of high area to mass ratio (HAMR) objects and other larger space debris.
Ground- and space-based optical observations of space objects rely on knowledge concerning how spacecraft materials interact with light. One common surface material for many currently active spacecraft is Kapton-HN® polyimide. Changes in optical signature for polymeric materials can occur due to surface degradation, leading to altered reflectivity, or due to radiation induced chemical modification, leading to an alteration of a material’s absorption/transmission properties. The optical fingerprints of commonly used materials change continuously under exposure to high energy electrons, a primary damaging species in geostationary Earth orbit (GEO). Laboratory observations show that these changes in a material’s optical signature are wavelength dependent and to some degree transient. This work investigates the changes in the optical reflection behavior of a variety of aerospace materials before and after electron irradiation. The results of this investigation will find use in the space debris remediation community for characterization of high area to mass ratio (HAMR) objects and other larger space debris.
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