While not specifically designed as a planetary mission, NASA’s Parker Solar Probe (PSP) mission uses a series of Venus gravity assists (VGAs) in order to reduce its perihelion distance. These orbital maneuvers provide the opportunity for direct measurements of the Venus plasma environment at high cadence. We present first observations of kinetic scale turbulence in the Venus magnetosheath from the first two VGAs. In VGA1, PSP observed a quasi-parallel shock, $\beta\sim1$ magnetosheath plasma, and a kinetic range scaling of $k^{-2.9}$. VGA2 was characterised by a quasi-perpendicular shock with $\beta\sim 10$, and a steep $k^{-3.4}$ spectral scaling. Temperature anisotropy measurements from VGA2 suggest an active mirror mode instability. Significant coherent waves are present in both encounters at sub-ion and electron scales. Using conditioning techniques to exclude these electromagnetic wave events suggests the presence of developed sub-ion kinetic turbulence in both magnetosheath encounters.

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. Our SPIS modeling relied on material properties of new spacecraft materials that we had obtained in previous work. 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). 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. 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. 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. The FIELDS antennas and shield also see this barrier forming but on a smaller scale. The FIELDS antennas charge positively at all distances modeled when no current bias is applied. Current biasing of the antennas affects their floating potential.

This research shows Part II of the Spacecraft Interaction Plasma Software (SPIS) used to model the Parker Solar Probe (PSP) FIELDS instrument and its interactions with the Solar Wind. Flight data was used to run the PSP model and compared with models using past predicted parameters. The effect of voltage biasing between the antenna, its shield, and the spacecraft on the current balance of each surface was investigated at first perihelion (0.16AU). The model data was reduced to I-V curves to find current saturations (analysis results 52µA versus flight results 54-72 µA), and sheath resistances (analysis results of 307 kΩ versus flight results of 51 kΩ). The recommended bias current to ensure optimal sensitivity of the FIELDS antenna was between -52 µA and -22 µA, which corresponded to a differential potential with respect to the spacecraft between -5V and 5V. The analysis also shows that plasma sheath of the FIELDS antenna and the plasma sheath of the FIELDS shield interacted between each other with an impedance of ~220kΩ.

No existing instrument is capable of consistently measuring all three components of the DC and low frequency electric field (E-field) throughout the heliosphere with sufficient accuracy to determine the smallest, and most geophysically relevant component: the E-field component parallel to the background magnetic field. E-field measurements in the heliosphere are usually made on spinning spacecraft equipped with two disparate types of double probe antennas: (1) long wire booms in the spin plane, and (2) ~10 times shorter rigid booms along the spin axis. On such systems, the potential difference (signal + noise) is divided by the boom length to produce a resultant E-field component. Because the spacecraft-associated errors are larger nearer the spacecraft, the spin plane components of the E-field are well measured while the spin axis component are poorly measured. As a result, uncertainty in the parallel E-field is usually greater than its measured value. Grotifer leverages more than fifty years of expertise in delivering highly accurate spin plane E-field measurements, while overcoming inaccuracies generated by spin axis E-field measurements. Its design consists of mounting detectors on two rotating plates, oriented at 90° with respect to each other, on a non-rotating central body. Each rotating plate has two component measurements of the E-field such that the Twin Orthogonal Rotating Platforms (TORPs) provide four instantaneous measurements of the E-field, and the three E-field components are well-measured by the rotating detectors. Grotifer (Giant rotifer) is a reference to the rotifer, also known as the “wheel animalcule”, which has twin crowns of antenna-like cilia that appear to rotate in all directions. Grotifer marks a profound change in E-field instrument design that represents the best path forward to close the observational gap that currently hampers resolution of significant science questions at the forefront of space plasma physics research. Here, we present the Grotifer design concept implemented as a 27-U CubeSat, discuss the important features in the design and operation of Grotifer, and demonstrate the feasibility of implementing Grotifer using existing sub-systems and technologies.

Depressions in magnetic field strength, commonly referred to as magnetic holes, are observed ubiquitously in space plasmas. Sub-proton-scale magnetic holes with spatial scales smaller than or on the order of $\rho_p$, are likely supported by electron currents vortices, rotating perpendicular to the ambient magnetic field. While there are numerous accounts of sub-proton-scale magnetic holes within the Earth’s magnetosphere, there are no reported observations in other space plasma environments. We present the first evidence of sub-proton-scale magnetic holes in the Venusian magnetosheath. During Parker Solar Probe’s first Venus Gravity Assist, the spacecraft crossed the planet’s bow shock and subsequently observed the Venusian magnetosheath. The FIELDS instrument suite onboard the spacecraft achieved magnetic and electric field measurements of magnetic hole structures. The electric field associated with magnetic depressions are consistent with electron current vortices with amplitudes on the order of 1 $\mu$A/m$^2$.