the Dust Impact sensor and the Langmuir Probe. Understanding of mechanisms of the dust electric charging, dust levitation and electric charging of a lander on the lunar surface is essential for interpretation of measurements of the instruments of the Luna-Glob lander payload, e.g. Resulted electric charge and thus surface potential depend on the lunar local time, latitude and the electrical properties of the regolith. The upper insulating regolith layer is electrically charged by the solar ultraviolet radiation and the flow of solar wind particles. One of the complicating factors of the future robotic and human lunar landing missions is the influence of the dust. Current biasing of the antennas affects their floating potential. The FIELDS antennas charge positively at all distances modeled when no current bias is applied. The FIELDS antennas and shield also see this barrier forming but on a smaller scale. At the same time, an electrostatic barrier forms near the illuminated surface of the TPS and reflects the photoelectrons back leading to negative charging of some surfaces. As the spacecraft approaches the Sun, the temperature of the TPS increases, the resistance between it and the spacecraft drops, and its photoemission increases, driving the spacecraft more positive. We find the following results: At greater distances from the Sun, the shadowed spacecraft charges negatively while the illuminated Thermal Protection System (TPS) charges positive due to the high resistance of the TPS Alumina shield at low temperatures. The model was used to find the floating potentials of the spacecraft and FIELDS antennas at different distances from the Sun (from 1AU to 0.046AU). Our SPIS modeling relied on material properties of new spacecraft materials that we had obtained in previous work.
The Spacecraft Interaction Plasma Software package (SPIS), a three‐dimension particle in cell (PIC) code, was used to model the Parker Solar Probe (PSP) spacecraft and FIELDS instrument and their interactions with the Solar wind.