The Psyche mission is a journey to a unique metal asteroid of the same name, (16) Psyche, orbiting the Sun between Mars and Jupiter. Psyche launched October 13 th , 2023 from Kennedy Space Center. The mission seeks to answer questions about the formation of planets and explore what may be an exposed nickel-iron core of an early planetesimal, similar to the one hidden at the center of our own Earth. The mission is led by Arizona State University. NASA's Jet Propulsion Laboratory is responsible for mission management, systems engineering, operations, navigation, and some subsystems including command and data handling and telecommunications. This paper focuses on the Psyche Payload System, which consists of a multispectral Imager, a Magnetometer, a Gamma-Ray and Neutron Spectrometer (GRNS), and a Deep Space Optical Communications (DSOC) experiment. The GRNS will measure the asteroid’s composition, the Magnetometer will determine whether Psyche is a core by measuring any remnant magnetic field, and the Imager will map its surface and characterize its topography. DSOC is a technology demonstration hosted by the Psyche spacecraft and intended to pave the way for low-power/high-bandwidth communications in deep space using individual photons to encode and transmit information. This paper focuses on the Payload development efforts and key systems engineering processes that made it possible including requirements development, risk reduction activities, key challenges and anomalies, verification and validation, and the final stretch to launch during assembly and test with the integrated spacecraft.

Abstract Paleomagnetic measurements of meteorites indicate that magnetic fields existed in the inner solar nebula capable of driving accretion at rates similar to those observed for young stellar objects with protoplanetary disks. However, the field strength in the solar system beyond ∼7 astronomical units (AU) and its role in accretion remain poorly constrained. Returned samples from asteroid (162173) Ryugu offer the possibility of determining the nebular field intensity in this distal region. Here, we report paleomagnetic studies of three Ryugu particles which reveal that alteration occurred in the presence of a null or relatively weak (<15.8 μT) field within 3 million years (Ma) after solar system formation. This resolves previously contrasting reports that Ryugu's parent body experienced alteration in the presence of a strong (>80 μT) magnetic field and weak or null field (<3 μT). In addition, we re‐examine previous paleomagnetic and Mn‐Cr chronometry studies of three other distally‐sourced meteorites, Tagish Lake, Tarda, and Wisconsin Range 91600, which measured paleointensities of <0.9, <1.7 and 5.1 ± 4.5 μT respectively. While it was previously unclear whether these records were acquired while the nebula was present, our re‐analysis suggests that their records are sufficiently old (i.e., <3.5 Ma after solar system formation) to be nebular in origin. Collectively, these data demonstrate that the distal solar system nebular field, while faint, was likely still strong enough to drive accretion at rates like those observed in the inner solar system.

The goal of NASA’s Europa Clipper Mission is to investigate the habitability of the subsurface ocean within the Jovian moon Europa using a suite of ten investigations. The Europa Clipper Magnetometer (ECM) and Plasma Instrument for Magnetic Sounding (PIMS) investigations will be used in unison to characterize the thickness and electrical conductivity of Europa’s subsurface ocean and the thickness of the ice shell by sensing the induced magnetic field, driven by the strong time-varying magnetic field of the Jovian environment. However, these measurements will be obscured by the magnetic field originating from the Europa Clipper spacecraft. In this work, a magnetic field model of the Europa Clipper spacecraft is presented, characterized with over 260 individual magnetic sources comprising various ferromagnetic and soft-magnetic materials, compensation magnets, solenoids, and dynamic electrical currents flowing within the spacecraft. This model is used to evaluate the magnetic field at arbitrary points around the spacecraft, notably at the locations of the three fluxgate magnetometer sensors and four Faraday cups which make up ECM and PIMS, respectively. The model is also used to evaluate the magnetic field uncertainty at these locations via a Monte Carlo approach. Furthermore, both linear and non-linear gradiometry fitting methods are presented to demonstrate the ability to reliably disentangle the spacecraft field from the ambient using an array of three fluxgate magnetometer sensors mounted along an 8.5-meter (m) long boom. The method is also shown to be useful for optimizing the locations of the magnetometer sensors along the boom. Finally, we illustrate how the model can be used to visualize the magnetic field lines of the spacecraft, thus providing very insightful information for each investigation.

The asteroid (16) Psyche is the target of the NASA Psyche mission, where the magnetometer is one of the three science instruments on board. Its purpose is to prove whether the asteroid formed from the core of a differentiated planetesimal. The magnetometer will measure the magnetic field at different distances from the asteroid in order to detect any remanent magnetization, where a magnetic moment larger than 2×10^14 Am2 could imply that the body once generated a core dynamo, and therefore formed as an igneous differentiation.The Psyche spacecraft carries two three-axis fluxgate magnetometers mounted on a fixed boom at 2.15m and 1.45m, respectively, which provide redundancy and gradiometer capabilities to compensate for spacecraft-generated magnetic fields. The magnetometers will be powered on early in the initial checkout phase and remain on throughout cruise and orbital operations and producing 50 vectors per second. The in-flight temperature of the magnetometers is expected to span a large range, therefore an extensive calibration program has been carried out in order to characterize the instruments and prove the performance pre-flight.

The objective of the Psyche Magnetometry Investigation is to test the hypothesis that asteroid (16) Psyche formed from the core of a differentiated planetesimal. To address this, the Psyche Magnetometer will measure the magnetic field around the asteroid to search for evidence of remanent magnetization. Paleomagnetic measurements of meteorites and dynamo theory indicate that a diversity of planetesimals once generated dynamo magnetic fields in their metallic cores. Likewise, the detection of a strong magnetic moment ( >2×10^14 Am^2 ) at Psyche would likely indicate that the body once generated a core dynamo, implying that it formed by igneous differentiation. The Psyche Magnetometer consists of two three-axis fluxgate Sensor Units (SUs) mounted 0.7 m apart along a 2.15-m long boom and connected to two Electronics Units (EUs) located within the spacecraft bus. The Magnetometer samples at up to 50 Hz, has a range of ±80,000 nT , and an instrument noise of 39 pT axis^-1 3σ integrated over 0.1 to 1 Hz. The two pairs of SUs and EUs provide redundancy and enable gradiometry measurements to suppress noise from flight system magnetic fields. The Magnetometer will be powered on soon after launch and acquire data for the full duration of the mission. The ground data system processes the Magnetometer measurements to obtain an estimate of Psyche’s dipole moment.

Energetic charged particles trapped in planetary radiation belts are hazardous to spacecraft. Planned missions to iron‐rich asteroids with possible strong remanent magnetic fields require an assessment of trapped particles energies. Using laboratory measurements of iron meteorites, we estimate the largest possible asteroid magnetic moment. Although weak compared to moments of planetary dynamos, the small body size may yield strong surface fields. We use hybrid simulations to confirm the formation of a magnetosphere with an extended quasi‐dipolar region. However, the short length scale of the field implies that energetic particle motion would be nonadiabatic, making existing radiation belt theories not applicable. Our idealized particle simulations demonstrate that chaotic motions lead to particle loss at lower energies than those predicted by adiabatic theory, which may explain the energies of transiently trapped particles observed at Mercury, Ganymede, and Earth. However, even the most magnetized asteroids are unlikely to stably trap hazardous particles.

Accurate measurements of ambient planetary and interplanetary magnetic fields using spacecraft magnetometers typically require accounting for interfering magnetic fields generated by the flight system (FS). The most common method for removing FS-generated time-variable magnetic fields is narrow-band and low-pass filtering of magnetic field data in the frequency domain. However, if fluctuations in the ambient field contain frequencies overlapping those in the FS field, it can be difficult to construct a filter that will not affect both signals. Here we present an alternate method for removing FS time-variable signatures from magnetic field measurements. For spacecraft that make use of a magnetic gradiometer (i.e. with two or more instruments on a boom at different distances from the center of the spacecraft), the dominant frequencies in the FS field can be identified using spectra of the differenced field components. The amplitudes of the FS field at those frequencies can then be suppressed without removing spectral peaks present in the ambient field. We demonstrate the successful application of this method, referred to as gradiometry peak suppression, both to modeled data sets and to 128 Hz Venus Express magnetometer data.

Psyche is a Discovery mission that will visit the asteroid (16) Psyche to determine if it is the metallic core of a once larger differentiated body or otherwise was formed from accretion of unmelted metal-rich material. The spacecraft will launch in August 2022 and arrive at the asteroid in January 2026. Psyche will carry three science instruments: a gamma ray and neutron spectrometer, a magnetometer, and a multi-spectral imager. Additionally, the spacecraft will host the Deep Space Optical Communications payload, which is a technology demonstration not required to meet Psyche's science objectives. The magnetometer is composed of two identical high-sensitivity magnetic field fluxgate sensors mounted in a gradiometer configuration that enables the rejection of meter-scale stray fields from the spacecraft. The instrument is key to meeting mission objectives since measurements of a strong asteroid remanent magnetic field will unambiguously indicate that (16) Psyche is an iron core. The magnetic signature from the spacecraft is the main source of noise for the magnetometer, both for DC and AC magnetic fields. Limiting and characterizing spacecraft-generated magnetic fields is therefore essential to the mission. This is the objective of the Psyche's magnetics control program described in this paper. The first step towards a successful program was to establish a set of magnetic cleanliness requirements directly derived from the magnetometer science performance and Psyche's range of expected fields. Test and modeling efforts of DC and AC fields of spacecraft components were then put in place to characterize and understand the spacecraft fields and enable verification of the cleanliness requirements. In this paper we describe the derivation of these requirements, test and analyses methods, and more generally the processes and procedures that govern the magnetics program for Psyche. The paper concludes with a discussion of the challenges and work to go and a comparison with the magnetic control processes of other missions with similar magnetic cleanliness constraints.

Author(s): Ream, Jodie Barker | Advisor(s): Walker, Raymond J; Ashour-Abdalla, Maha | Abstract: Pi2 pulsations are magnetic field fluctuations with periods between 40 an 150 seconds observed on the ground in conjunction with the onset of magnetospheric substorms. Pi2 period perturbations are also observed in magnetic field and plasma observations in space in conjunction with fast earthward flows leading to several theories concerning how and where the pulsations are generated. We investigate the source and propagation of Pi2 period pulsations through the magnetosphere, tracing the disturbances from their origin in the magnetotail through the inner edge of the plasma sheet and into the inner magnetosphere. Several models for the generation of Pi2 pulsations have been constructed by using satellite and ground-based observations. Our approach is to use global magnetohydrodynamic (MHD) computer codes to simulate the Earth's magnetosphere during substorms to determine where the Pi2 period perturbations are being generated. We use two different MHD models, the UCLA and Lyon-Fedder-Mobarry (LFM) models, in order to test the robustness of our conclusions about Pi2. The simulation results are compared with ground-based and satellite data for validation. We find that Pi2 period perturbations are generated in both models by earthward propagating fast flows inside of x~-12 RE. As the flows propagate through the braking region, the region where flows slow down as they approach the inner edge of the plasma sheet, the pulsations begin to run ahead of the fast flow and its accompanying dipolarization front into the inner magnetosphere. This indicates that a compressional wave is being generated by the flow as it slows in the braking region. The speed of the flows, and the penetration of the flows and perturbations into the inner magnetosphere, depends strongly on the ionospheric models used at the inner boundary of the MHD models. When modeled Pedersen conductances are high with respect to typically observed values, strong line-tying slows the flows more quickly in the braking region. Therefore, perturbations are not able to propagate as freely into the inner magnetosphere.When looking at the power spectral density (PSD) we find that the fluctuations in Bz propagate with the flow channel until they reach ~-8 RE, but as the disturbance approaches the inner edge of the plasma sheet the flow speeds decrease and the perturbations propagate earthward and spread azimuthally. As a result the perturbations generated by an azimuthally thin flow channel would be observed over a large area on the ground. Field line tracing shows that ionospheric perturbations do not always map to a flow channel, but they do map to a disturbance in the thermal pressure associated with the flow. Since the flows are responsible for the thermal pressure perturbations, they are also indirectly responsible for the perturbations observed in the simulated ionosphere.