We present theoretical estimates of the electrical charge and electrostatic surface potentials on debris objects orbiting in the LEO and GEO regions of the Earth's ionosphere. The estimates are ...obtained using analytic calculations based on an improved Orbital Motion Limited model as well as through numerical Particle-In-Cell simulations using the open-source SPIS code. A variety of shapes, sizes, and material compositions of the debris objects are considered, including HAMR objects with a high area-to-mass ratio and objects composed of insulating and conducting material patches. In the GEO region, we consider the charging arising from photo-emission effects and the impact of energetic charged particle beams associated with solar flares. We discuss the nature of the debris-induced collective excitations in the plasma and their potential use for debris detection.
•Measurement of charge and surface potential on space debris in LEO and GEO regions.•Comparison of debris charging using OML theory and Particle-In-Cell simulations.•Collective excitations due to charged debris.
Spacecraft charging is problematic for low‐energy plasma measurements. The charged particles are attracted to or repelled from the charged spacecraft, affecting both the energy and direction of ...travel of the particles. The Ion Composition Analyzer (RPC‐ICA) on board the Rosetta spacecraft is suffering from this effect. RPC‐ICA was measuring positive ions in the vicinity of comet 67P/Churyumov‐Gerasimenko, covering an energy range of a few eV/q to 40 keV/q. The low‐energy part of the data is, however, heavily distorted by the negatively charged spacecraft. In this study we use the Spacecraft Plasma Interaction Software to model the influence of the spacecraft potential on the ion trajectories and the corresponding distortion of the field of view (FOV) of the instrument. The results show that the measurements are not significantly distorted when the ion energy corresponds to at least twice the spacecraft potential. Below this energy the FOV is often heavily distorted, but the distortion differs between different viewing directions. Generally, ions entering the instrument close to the aperture plane are less affected than those entering with extreme elevation angles.
Plain Language Summary
The Rosetta spacecraft followed comet 67P/Churyumov‐Gerasimenko for 2 years, providing data giving new insights into the nature of comets. The Ion Composition Analyzer (RPC‐ICA) on board the spacecraft measures positive ions in the vicinity of the comet. The instrument can measure low‐energy ions, which play an important part in the processes taking place in this environment. To fully understand the environment around the comet, we have to understand these low‐energy ions. Unfortunately, this part of the RPC‐ICA data is distorted by the spacecraft potential. A spacecraft in space interacts with the surrounding environment, which charges the spacecraft surface to a positive or negative potential. Rosetta was commonly charged to a negative potential throughout the mission, which means that the positive ions measured by RPC‐ICA were attracted to the spacecraft. Consequently, both the energy and the travel direction of the ions changed before detection. We investigate how the low‐energy ions measured by RPC‐ICA have been affected by the spacecraft potential. We use the Spacecraft Plasma Interaction Software to model these effects. The results give us a lower energy limit above which we can trust the measurements and show that some parts of the instrument are more heavily affected than others.
Key Points
We model the influence of the spacecraft potential on low‐energy ion measurements made by the Ion Composition Analyzer on board Rosetta
The field of view of the instrument is heavily distorted for some energies and viewing directions
The direction measurements can be trusted when the ion energy corresponds to at least twice the spacecraft potential
PDF
