We report new measurements of high-energy protons ejected by the sun during the May 2024 Ganon superstorm. Our observations were made by the Neutron Spectrometer (NS) on the Psyche spacecraft, which was located at a solar distance of approximately 2 AU and a Sun-Earth-Probe separation angle of 75 degrees. This unique vantage point can provide new insights into the nature of this exceptional space weather event. Our observations validated predictions from the WSA-ENLIL heliospheric model, which forecasted that the Psyche spacecraft would be magnetically-connected to the Coronal Mass Ejection (CME) on May 10th-11th, and that the Psyche spacecraft would pass through the periphery of the proton-rich region driven by the superstorm's CME on May 13th. This agreement both validates the large-scale CME propagation predicted by ENLIL and underscores the value of observations from a variety of geometries. The Psyche spacecraft will continue to make unique observations of solar particle events throughout its interplanetary cruise to asteroid 16 Psyche. We believe that these observations will be a valuable resource for refining particle-transport models and improving forecasts of solar energetic proton arrival times and intensities.

The period 2023 to 2024 corresponded to the ascending phase of the solar cycle, which was a suitable time to observe the solar events. During this period, we reported the radiation doses and dose quantities measured on four large solar energetic particle (SEP) events (July 18, 2023, February 10, 2024, May 11, 2024, and June 8, 2024). A silicon-based particle dosimeter as a science payload was launched on May 25, 2023, onboard the Next Generation small satellite-2 (NEXTSat-2). Each SEP event showed different dose rates and quality factors between 1.7 and 2.3, depending on the spectrum shape. The event on July 8, 2024 showed the highest absorbed dose rate of about 2200 mu Gy/h. From July 1 to October 31, 2023, and from February 1 to July 31, 2024, galactic cosmic rays (GCR) and trapped protons in the South Atlantic Anomaly (SAA), which are relatively constant radiation sources over time, showed a decreasing trend during the observation. The average absorbed dose rate of GCR and trapped protons in the SAA was 5.42 f 0.32 mu Gy/h and 1900.76 f 166.18 mu Gy/h, respectively. The average quality factor was 4.46 f 0.12 and 1.55 f 0.01, respectively. This study first provided the biologically effective doses to humans in the high-altitude low-Earth orbit (LEO) region at an altitude of 550 km with an inclination of 97.8 degrees. Further, we demonstrated that the space environment model-based simulations produced the results comparable to the measurements although the results varied from model to model used in the simulations. The long-term accumulation of the data in various altitudes of LEO over a solar cycle could be used to update the models in the future.

The Psyche spacecraft launched on October 13, 2023 to journey to the asteroid of the same name. Psyche is the largest M-class asteroid and possibly the remanent core of an early differentiated planetesimal that was disrupted by collisions. The Psyche mission will test that hypothesis as the 14th mission in NASA’s Discovery Program. An alternative hypothesis is that the asteroid is unmelted primordial material. We describe the proposal competition process leading to selection of the mission and its context with other small body missions. This paper will briefly introduce the three science instruments, gravity science investigation, and Deep Space Optical Communications technology demonstration, leading into a detailed explanation of the science mission architecture. The orbital science phase is divided into a series of circular mapping orbits at four distinct altitudes, each selected to address specific science objectives. The requirements and objectives for each orbit are accompanied by an assessment of the effectiveness of each phase. We discuss the structure of the Psyche team during the operations phase along with the roles and responsibilities of the science and flight operations teams. Key elements of mission operations that are unique to the Psyche mission are provided. The Science Data Center manages and archives the Psyche mission data. The contents of the archive data sets for each instrument are outlined as well as the interfaces between the Science Data Center, the instrument teams, and the Planetary Data System.

A Gamma-Ray and Neutron Spectrometer (GRNS) instrument has been developed as part of the science payload for NASA’s Discovery Program Psyche mission to the M-class asteroid (16) Psyche. The GRNS instrument is designed to measure the elemental composition of Psyche with the goal to understand the origin of this mysterious, potentially metal-rich planetary body. The GRNS will measure the near-surface abundances for the elements Ni, Fe, Si, K, S, Al, and Ca, as well as the spatial distribution of Psyche’s metal-to-silicate fraction (or metal fraction). These measurements address three of the five Psyche mission science objectives: determine if Psyche is a core; determine whether small metal bodies incorporate light elements into the metal phase; and determine whether Psyche was formed under reducing conditions. The Gamma-Ray Spectrometer (GRS) uses a cryocooled, high-purity Ge (HPGe) sensor to detect cosmic-ray generated gamma rays in the 60 to 9000-keV energy range. The HPGe sensor is surrounded by a borated plastic anticoincidence shield that provides three functions: active background rejection from charged particle interactions in the HPGe sensor; fast neutron measurements; and direct measurements of the incident galactic cosmic ray flux. The Neutron Spectrometer (NS) uses three 3He gas proportional sensors, each with different material wraps to measure thermal (<0.4 eV), low-energy epithermal (0.4 eV to 1 keV), and high-energy epithermal (up to 100 keV) neutrons. This paper provides an overview of the Psyche GRNS, including: its science and measurement objectives; the design of the instrument hardware, software, and operation; pre-launch performance measurements and its initial performance in space; and an overview of its data products and expected operation for different Psyche mission phases.

To assess the biological effects of lunar surface radiation, two silicon-based detectors, a dosimeter and a spectrometer, were developed as science payloads for the Commercial Lunar Payload Services (CLPS) program. They were designed to measure the linear energy transfer (LET) and energy spectra of charged particles originating from galactic cosmic rays (GCRs) and solar energetic particles (SEPs). The dosimeter uses a thick and a thin silicon sensor to measure lower and higher LET particles, respectively. The spectrometer uses the same silicon sensors and adds a cesium iodide (CsI) scintillator behind them, followed by a third silicon sensor. They were tested with the He, C, Si, and Fe ion beams modulated by different thicknesses of polymethyl methacrylate (PMMA) at the Heavy Ion Medical Accelerator in Chiba (HIMAC) to simulate heavy ions with a wide range of LET present on the lunar surface. Monte Carlo simulations were performed with the same geometry as the experimental setup to calibrate the analog-to-digital converter (ADC) channels of the sensors to LET values. A fairly linear relationship was observed between the measured peak channels and the simulated LET values across a broad LET range. However, a slight deviation from linearity was observed in the high LET region for the heavily modulated Fe ion beams. The energy calibration of the spectrometer showed that the incident proton energies could be reconstructed from the energy deposits in the stacked sensors. These results indicate that the developed dosimeter and spectrometer are suitable for measuring the LET and energy spectra of charged particles from GCRs and SEPs on the lunar surface and can provide valuable information on the biological effects of lunar surface radiation.

Space weather is a multidisciplinary research area connecting scientists from across heliophysics domains seeking a coherent understanding of our space environment that can also serve modern life and society's needs. COSPAR's ISWAT (International Space Weather Action Teams) 'clusters' focus attention on different areas of space weather study while ensuring the coupled system is broadly addressed via regular communications and interactions. The ISWAT cluster "H3: Radiation Environment in the Heliosphere" (https://www.iswat-cospar.org/h3) has been working to provide a scientific platform to understand, characterize and predict the energetic particle radiation in the heliosphere with the practical goal of mitigating radiation risks associated with areospace activities, satellite industry and human space explorations. In particular, present approaches help us understand the physical phenomena at large, optimizing the output of multi-viewpoint observations and pushing current models to their limits. In this paper, we review the scientific aspects of the radiation environment in the heliosphere covering four different radiation types: Solar Energetic Particles (SEPs), Ground Level Enhancement (GLE, a type of SEP events with energies high enough to trigger the enhancement of ground-level detectors), Galactic Cosmic Rays (GCRs) and Anomalous Cosmic Rays (ACRs). We focus on related advances in the research community in the past 10-20 years and what we still lack in terms of understanding and predictive capabilities. Finally we also consider some recommendations related to the improvement of both observational and modeling capabilities in the field of space radiation environment.

The natural space environment exerts many harmful (called “space weather”) effects on spacecraft in orbit around the Earth as well as probes to other planets. The main hazards among these are surface charging, internal charging, single event effects, and total dose. Specifically, the ∼keV electron population can have substantial impacts on spacecraft by causing spacecraft surface charging and electrostatic discharges (ESD). This hazard continues to be of great relevance today due to the continual evolution of the human use of space in terms of the number of satellites launched, the technologies they use and the design / manufacturing / test techniques used to build them. In the past, the majority of operating spacecraft were in Geosynchronous Earth Orbit (GEO), nowadays the Low-Earth orbit (LEO) satellite population dominates and the number of Non-Geostationary Satellite Orbit (NGSO) constellations increases; these new constellations are likely to increase the technical risks associated with harmful space weather conditions. This paper summarizes the state of art for surface charging including background of the phenomenon, data sources for characterizing charging on spacecraft, modeling of the space weather environment, surface charging modeling tools, and charging indices and metrics. Future directions and both near- and long-term recommendations are also provided.

Space radiation affects every aspect of spacecraft design and operation. As a part of the ISWAT (International Space Weather Actions Teams, http://iswat-cospar.org/) effort, this paper provides a comprehensive review of space radiation environment models that are commonly used by the spacecraft design community to estimate radiation effects on systems/components. The types of radiation effects discussed in this paper are total dose (both for ionizing and for non-ionizing), single event effects (SEE), surface and internal charging, and radiation effects at aviation altitudes. For each effect, a brief overview of the effect is described, relevant environment models are discussed, and the currently understood gaps and future needs are summarized. This paper serves as the radiation environment pathway-to-impact paper in the overall ISWAT Roadmap development.

The Near-Earth Space Radiation and Plasma Environment falls within the realm of G3 Cluster (G3 refers to ‘Near-Earth Radiation and Plasma Environment’ of the ‘Coupled Geospace System’) under the COSPAR (Committee On Space Research) /International Space Weather Action Teams (ISWAT) Initiative. The diverse and dynamic particle populations from this region pose challenges from both science and space weather-impact perspectives. The G3 cluster has intimate connections with solar, heliosphere clusters, and the other Geospace ones (G1, G2) through a chain of physical processes. This paper reviews recent scientific advances in understanding this complex space environment, identifies gaps in research and space weather applications, and maps out our recommendations on priorities for the next 5-10 years.

This article describes the nowcast of aerospace radiation system (NAIRAS) model, which is now publicly available at the Community Coordinated Modeling Center (CCMC). NAIRAS predicts dosimetric and radiation flux quantities for assessing human radiation exposure and radiation effects to flight vehicle electronic systems from the surface of the Earth to deep space. NAIRAS predictions of the ionizing radiation environment are shown for various space weather conditions in the atmosphere and in low-Earth orbit (LEO), medium-Earth orbit (MEO), and cislunar orbit. NAIRAS model comparisons with dosimeter measurements are presented for aircraft and various spaceflight platforms.

Jupiter's icy moon, Europa, harbors a subsurface liquid water ocean; the prospect of this ocean being habitable motivates further exploration of the moon with the upcoming NASA Europa Clipper mission. Key among the mission goals is a comprehensive assessment of the moon's composition, which is essential for assessing Europa's habitability. Through powerful remote sensing and in situ investigations, the Europa Clipper mission will explore the composition of Europa's surface and subsurface, its tenuous atmosphere, and the local space environment surrounding the moon. Clues on the interior composition of Europa will be gathered through these assessments, especially in regions that may expose subsurface materials, including compelling geologic landforms or locations indicative of recent or current activity such as potential plumes. The planned reconnaissance of the icy world will constrain models that simulate the ongoing external and internal processes that act to alter its composition. This paper presents the composition-themed goals for the Europa Clipper mission, the synergistic, composition-focused investigations that will be conducted, and how the anticipated scientific return will advance our understanding of the origin, evolution, and current state of Europa.

A particle dosemeter (PD) is a payload of NEXTSat-2 in the low-earth orbit (LEO). The absorbed dose in LEO needs to be converted into the ambient dose equivalent (H*(10)). Due to a mixed field in LEO, the calibration factors (klow and khigh) should be determined for the low-and high-linear energy transfers (LET) (below and above 1.5 keV/μm), respectively. The PD was irradiated with a 137Cs source at the Korea Radiation Solution facility to obtain H*(10) and absorbed doses. However due to the lack of sources for the high-LET calibration, H*(10) and an absorbed dose were calculated by simulating PD for the high-energy neutron field at CERN-EU high-energy Reference Field. The measured klow of PD had a difference of 5.1% and 9.5% from the calculated value of PD and the measured value of Liulin detectors, respectively. However, a difference in khigh between PD and Liulin was explained by the contribution of non-neutron components to Liulin in the measurements.

We present an overview of the radiation environment monitoring program planned for the Europa Clipper mission. The harsh radiation environment of Jupiter will be measured by a dedicated Radiation Monitor (RadMon) subsystem, yielding mission accumulative Total Ionizing Dose (TID) and instantaneous electron flux measurements with a 1-Hz cadence. The radiation monitoring subsystem is comprised of a stand alone sensor assembly along with distributed TID assemblies at various locations on the spacecraft. The sensor assembly itself is made of a TID sensor stack using the Metal-Oxide Semiconducting Field-Effect Transistor (MOSFET) and a Charge Rate Monitor (CRM) that uses a stack of bulk charge collection plates. The TID measurements will provide the critical information about the overall radiation levels relevant to the degradation of electronics over time, and the electron flux data can serve as a proxy for the Internal ElectroStatic Discharge (IESD) environment by measuring the >∼1 MeV electron environment. In addition, the radiation monitoring subsystem data will be augmented by serendipitous radiation data from science instruments onboard. This will be enabled by careful modeling and analysis of opportunistic background data from potentially the following instruments: Europa Imaging System (EIS), Europa-Ultraviolet Spectrograph (Europa-UVS), Mapping Imaging Spectrometer for Europa (MISE), MAss Spectrometer for Planetary EXploration (MASPEX), Plasma Instrument for Magnetic Sounding (PIMS), and SUrface Dust Analyzer (SUDA). Based on the current analysis, these instruments will be most sensitive to >1 MeV electrons. As such, the high-energy electron data obtained by the radiation monitoring subsystem will be qualitatively and quantitatively enhanced by the high-energy electron data acquired by the instruments. The holistic radiation monitoring program for the mission will be an extensive collaboration among many teams across the flight and payload systems. Although the radiation monitoring subsystem itself is an engineering resource for the mission, the collective data from the mission can also be used to improve the scientific understanding of the Jovian magnetosphere and the high-energy electron environment near Europa, where the motion of charged particles is perturbed by the local electromagnetic environment. The data could also help in the understanding of the radiation modification of Europa surface compounds, which could subsequently help guide lab experiments to aid in understanding the origin and evolution of surface materials and in constraining the interpretation of observational data. To this end, the radiation monitoring subsystem is a useful resource for helping address the Europa Clipper mission’s primary goal of assessing the habitability of Europa.

Abstract The Nowcast of Aerospace Ionizing RAdiation System (NAIRAS) version 3 model is available to the community through the Community Coordinated Modeling Center run‐on‐request (RoR) service. The RoR capability allows the user to run the NAIRAS model for customized applications and time‐periods using two run options. The global dosimetric run option mirrors the execution of the real‐time NAIRAS run mode. This class of run option capability provides global context and situational awareness of the atmospheric ionizing radiation environment. The flight trajectory run option allows the user to upload an aircraft, balloon, or spaceflight trajectory file. This class of run option allows detailed human radiation flight exposure characterization, detailed comparisons to onboard dosimeters, and the assessment of single event effects (SEE) in aircraft and spacecraft electronic systems. The model output includes dosimetric quantities, differential and integral flux, and fluence quantities. The flux and fluence quantities are a new feature in version 3 for the assessment of SEE. The trajectory run option and the extension of the model domain to the space environment is also a new feature in version 3.

Understanding the long‐term radiation environment at the surface of Mars allows us to estimate the exposure for future robotic and crewed missions. Typically, the radiation environment includes charged particles (i.e., protons and heavier ions) and neutral particles (i.e., gamma rays and secondary neutrons). Previous studies used in‐situ measurements, models, or both to determine the characteristics of the radiation at Mars. For example, the Mars Science Laboratory instrument, the Radiation Assessment Detector (RAD), has provided invaluable in‐situ data since landing in 2012. However, the RAD instrument is only sensitive to neutrons with energies > ∼6 MeV and therefore misses what is expected to be a substantial flux of lower‐energy neutrons. To address this gap, we have developed an approach to derive the surface neutron spectrum using the MSL RAD data augmented by orbital data from the High Energy Neutron Detector (HEND) onboard Mars Odyssey (neutron energy < ∼10 MeV). Using a power law fit, we determine neutron flux spectra that reproduce the measurements recorded by both RAD and HEND. Our approach involves a series of Monte Carlo simulations to develop a set of atmospheric transmission functions that enables us to convert the on‐orbit HEND data to their corresponding surface neutron flux spectra. The combined RAD—HEND data present a unique opportunity to obtain a complete picture of the surface neutron environment.

High energy protons from solar energetic particle (SEP) events are a hazard to spacecraft systems and instruments. For interplanetary and geosynchronous-Earth-orbiting spacecraft, a mission's cumulative SEP fluence is an important consideration for hardware design. The total solar proton fluence for a mission can be dominated by a small number of very high-fluence events. Because of the sporadic and unpredictable nature of these large events, data sets collected over multiple solar cycles are needed to construct a statistical model that can predict a mission's risk of seeing a given fluence exposure during its mission. Several statistical models have been developed, including the JPL model and the Emission of Solar Protons (ESP) model. The models produce somewhat different results, which could be due in part to the different data sets from which they were derived. To understand the sensitivity of predicted mission fluence to the choice of data set and to the statistical distribution to which that data set is fit, we present a comparison of the JPL and ESP cumulative fluence models as reformulated from the same SEP data set, a background-subtracted version of the Reference Data Set Version 2.0 (RDSv2.0) based on data from IMP-8 and GOES, covering 41 years of SEP events from 1974 to 2015 with proton energies between 5 and 289 MeV. The comparisons show that different modeling approaches can produce a factor of 2 or greater difference in the mission fluences even when the same data set is used for model development.

Until the arrival of Juno at Jupiter in 2016, the inner electron radiation belt dynamics has been examined from ground-based observations of Jupiter’s Synchrotron Emission (JSE) and theoretical modeling of the relativistic electron population. Simulations of JSE variability on month-to-year timescales only confirm a partial control of the Jovian Electron Radiation Belt (JERB) by large-scale solar-wind-driven particle transport. Juno prime mission and first years of the extended mission provide unique measurements of JSE from within JERB environment allowing us to further address the origins of JSE variability on a timescale of months. In the present work, we use Juno MicroWave Radiometer (MWR) data from mid-2016 to mid-2022 at different wavelengths to support our investigation of the origins of JERB dynamical behavior. Juno/MWR data from NASA Planetary Data System, ground-based observations of Jupiter and simulated Heliospheric Environment (HE) at the giant planet are combined to constrain the modeling of long-term variability of JSE as it would be observed from Earth. The Juno-data constrained trend of JSE at 11.5-cm wavelength is combined with single-dish observations to cover a multi-decade observation period. Using a simulator of JSE that accounts for the influence of physical parameters on jovian electron belts distributions, we present simulations of JSE to discuss the connection between JERB and HE and identify the magnetospheric physical processes (e.g., particle source and transport, interactions with planetary environment) which might have controlled JSE for the period 1962-2022. Acknowledgments: Key data processing, JERB model improvements and simulations of Juno/MWR measurements are carried out at Southwest Research Institute and primarily funded by NASA NFDAP program. This work benefits from collaborations with various Juno instrument teams and also from a larger science community.

The habitability of Europa is a property within a system, which is driven by a multitude of physical and chemical processes and is defined by many interdependent parameters, so that its full characterization requires collaborative investigation. To explore Europa as an integrated system to yield a complete picture of its habitability, the Europa Clipper mission has three primary science objectives: (1) characterize the ice shell and ocean including their heterogeneity, properties, and the nature of surface-ice-ocean exchange; (2) characterize Europa's composition including any non-ice materials on the surface and in the atmosphere, and any carbon-containing compounds; and (3) characterize Europa's geology including surface features and localities of high science interest. The mission will also address several cross-cutting science topics including the search for any current or recent activity in the form of thermal anomalies and plumes, performing geodetic and radiation measurements, and assessing high-resolution, co-located observations at select sites to provide reconnaissance for a potential future landed mission. Synthesizing the mission's science measurements, as well as incorporating remote observations by Earth-based observatories, the James Webb Space Telescope, and other space-based resources, to constrain Europa's habitability, is a complex task and is guided by the mission's Habitability Assessment Board (HAB).

&lt;p&gt;The Jupiter Energetic Particle Detector Instrument (JEDI) on the Juno mission detects energetic electrons from the tens of keV to almost 1 MeV and energetic ions from the tens of keV to about 10 MeV or more. The population at higher energies, e.g., &gt; 1 MeV electrons, while relatively small in number can add non-insignificant counts in the energy range JEDI is designed to detect as foreground. For example, a band is often seen in the electron spectrograms around 200 keV that is believed to be due to higher energy electrons that for various reasons only deposit a fraction of their energy in the detector. To apply a correction to this, Mauk et al. [JGR, 2018] have developed a procedure for correcting the JEDI-measured electron spectra contaminated with high-energy foreground electrons that penetrate the detector. Using this procedure, one can extract an energy spectrum from the tens of keV to 1 MeV that corrects for both penetrators and the loss of JEDI efficiency just below 1 MeV. The corrected spectra can also be extended above 1 MeV by making use of the penetrator counts, but uncertainties exist in creating a high-energy tail. &amp;#160;In addition, JEDI proton data may also be contaminated with ions. To extract accurate electron spectra that extend to high energies and understand the response to penetrating protons, one would need to better understand the response of the detector to those high-energy electrons and protons. Characterization of energetic particles above 1 MeV can enable a study of energetic particles&amp;#8217; dynamics and structure&lt;strong&gt; &lt;/strong&gt;as a function of latitude and L-shell and help evaluate different theories for loss and acceleration mechanisms. It is also a critical step in reducing uncertainties in the Jovian radiation models, assisting in understanding Juno data, and impacting future missions to Jupiter.&lt;/p&gt; &lt;p&gt;A series of comprehensive and realistic Geant4 simulations have been performed to obtain the Geometric Factors (GFs) of JEDI as functions of the energy and the angles of incoming electrons and protons at a breadth that is not feasible through laboratory measurements. The results of the simulations are presented in this paper. The GFs are used to convert the count rate measurements to more physically meaningful particle flux spectra. Here, we also show the long-term trend of thus-obtained electron and proton spectra during Juno&amp;#8217;s PJ 1 to 24.&amp;#160;&amp;#160;&lt;/p&gt;