Spacecraft charging of JUICE in the auroral zone of Ganymede

<p>Ganymede is the only moon in our Solar System known to have its own global magnetic field, which generates a miniature moon magnetosphere inside the Jovian magnetosphere. Due to this unique characteristic of Ganymede, its auroral zone is also of particular scientific interest, as it is the only known example of this specific kind of interaction. The JUICE spacecraft will orbit Ganymede for almost a year, with a high inclination orbit with multiple auroral zone crossings. JUICE will study the auroral zone of Ganymede in more detail than ever before, providing both in-situ and remote sensing observations.</p> <p>In this work, we use Spacecraft Plasma Interaction Software (SPIS) simulations to study the spacecraft charging of JUICE in the auroral zone. Hubble Space Telescope observations of the aurora of Ganymede show localized regions of bright spots superimposed on a continuous background emission (e.g. Feldman et al. 2000, Eviatar et al. 2001). In order to produce bright auroras, the electron population needs to be accelerated up to hundreds of eV (Eviatar et al. 2001). Preliminary simulation results, using an auroral electron population with temperature T<sub>e</sub> = 200 eV and density n<sub>e</sub> = 300 cm<sup>-3</sup>, shows frame charging (i.e. spacecraft ground) of around 10 V and differential charging of around 30 V. High frame and differential potentials can cause disturbances in both particle and electric field measurements and prevent accurate characterization of the environment. Since the auroral zone of Ganymede is of particular scientific interest, it is important to study and prepare for this kind of disturbances.</p> <p> </p> <p>References</p> <p>D. Feldman et al., HST/STIS ultraviolet imaging of polar aurora on Ganymede, The Astrophysical Journal, 535(2), 2000</p> <p>A. Eviatar et al., Excitation of the Ganymede ultraviolet aurora, The Astrophysical Journal, 555(2), 2001</p>

BepiColombo: A Platform for Improving Modeling of Electric Propulsion-Spacecraft Interactions

This article provides the first results of a long-term study aimed at improving the validity of numerical modeling techniques for Electric Propulsion induced Spacecraft Charging using the Spacecraft Plasma Interaction System software. The preflight numerical model of the European Space Agency’s BepiColombo mission and its outputs are presented as a benchmark example of the present capabilities and limitations of the model. It is demonstrated that the code can obtain the spacecraft charging equilibrium by simulating the dynamic interactions between the electric propulsion system, the thruster-generated plasmas, and spacecraft systems exposed to space. The importance of including a physical description of the electron cooling in the freely expanding thruster plasmas is shown by comparing simulations with different polytropic indexes. It particularly highlights the inadequacy of treating the entire plasma as isothermal. The reported variability of the simulation outputs with numerical and physical parameters paves the way for future improvements in preflight design modeling and increased understanding of plasma thruster-induced charging processes through future comparison with available flight telemetries.

Development of space environment customized risk estimation for satellites (SECURES)

Plasma variations in the geospace environment driven by solar wind–magnetosphere interactions are one of the major causes of satellite anomaly. To mitigate the effect of satellite anomaly, the risk of space weather disturbances predicted by space weather forecasting needs to be known in advance. However, the risk of satellite anomaly owing to space weather disturbances is not the same for all satellites, because the risk depends not only on the space environment itself but also on the design and materials of individual satellites. From the viewpoint of satellite operators, it is difficult to apply a general alert level of the space environment to the risk of individual satellites. To provide tailored space weather information, we have developed SECURES (Space Environment Customized Risk Estimation for Satellites) by combining models of the space environment and those of spacecraft charging. In SECURES, we focus on the risk of spacecraft charging (surface/internal) for geosynchronous satellites. For the risk estimation of surface charging, we have combined the global magnetosphere magnetohydrodynamics (MHD) model with the satellite surface charging models. For the risk estimation of internal charging, we have combined the radiation belt models with the satellite internal charging models. We have developed prototype products for both types of charging/electrostatic discharge (ESD). The development of SECURES and our achievements are introduced in this paper.

Development of Space Environment Customized Risk Estimation for Satellites (SECURES)

Plasma variations in the geospace environment driven by solar wind–magnetosphere interactions are one of the major causes of satellite anomaly. To mitigate the effect of satellite anomaly, the risk of space weather disturbances predicted by space weather forecasting needs to be known in advance. However, the risk of satellite anomaly owing to space weather disturbances is not the same for all satellites, because the risk depends not only on the space environment itself but also on the design and materials of individual satellites. From the viewpoint of satellite operators, it is difficult to apply a general alert level of the space environment to the risk of individual satellites. To provide tailored space weather information, we have developed SECURES (Space Environment Customized Risk Estimation for Satellites) by combining models of the space environment and those of spacecraft charging. In SECURES, we focus on the risk of spacecraft charging (surface/internal) for geosynchronous satellites. For the risk estimation of surface charging, we have combined the global magnetosphere magnetohydrodynamics (MHD) model with the satellite surface charging models. For the risk estimation of internal charging, we have combined the radiation belt models with the satellite internal charging models. We have developed prototype products for both types of charging/electrostatic discharge (ESD). The development of SECURES and our achievements are introduced in this paper.