Abstract Exposure to ionizing radiation from galactic cosmic rays and solar energetic particles at aviation flight altitudes can have an adverse effect on human health. Although airline crews are classified as radiation workers by the International Commission on Radiological Protection (ICRP), in most countries, their level of exposure is unquantified and undocumented throughout the duration of their career. As such, there is a need to assess aviation crew ionizing radiation exposure. The Nowcast of Aerospace Ionizing RAdiation System (NAIRAS) is a real‐time, global, physics‐based model currently used to assess such exposure. To evaluate recent model updates, radiation measurements from the Automated Radiation Measurements for Aerospace Safety (ARMAS) flight inventory are utilized. The inventory contains 1,324 flights at typical commercial aviation cruising altitudes during the most recent solar cycle, and covers latitudes 85°N to 85°S. Overall, while NAIRAS dose rates are uniformly biased high relative to the ARMAS dosimeter measurements, there is no bias relative to solar activity. Inspection of the model differences suggests that the TS05 magnetospheric magnetic field model may produce cutoff rigidities that are too low during quiet geomagnetic periods, particularly at mid‐to‐low latitudes, resulting in higher dose rates in NAIRAS. The difference in the altitude unit is also a source of error; the ARMAS flight database reports aircraft altitudes in GPS coordinates, while barometric pressure altitudes are required for NAIRAS. Future aircraft flights are being designed to constrain the uncertainties in the dosimetric measurements and model calculations.

In Low Earth Orbit (LEO), atmospheric drag is the largest contributor to trajectory prediction error. The current thermospheric density model used by the Combined Space Operations Center (CSpOC) in operations is the High Accuracy Satellite Drag Model (HASDM). Since HASDM is not available for use outside of the US Government, satellite operators are left to determine what publicly available, open-source density model they should integrate into their internal operational software. Given the ever more challenging nature of operations in LEO, it is imperative for satellite operators to update legacy density models to a state-of-the-art density model to provide improved trajectory predictions for collision risk assessment and vital day-to-day operational decisions. This article outlines four operations-ready thermospheric density models, describing their performance, computation time, required space weather inputs, and notes for implementation. Operations-ready models include the Drag Temperature Model (DTM), the Jacchia-Bowman 2008 (JB2008) model, the US Naval Research Laboratory Mass Spectrometer and Incoherent Scatter radar 2.0 (NRLMSIS 2.0) model, and the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). US Government operational density models, HASDM and the Whole Atmosphere Model and Ionosphere Plasmasphere Electrodynamics (WAM-IPE) model, are included for comparison. Models are evaluated against global HASDM density and local GRACE-FO satellite accelerometer densities and Swarm mission densities. Additionally, comparisons between HASDM and WAM-IPE nowcast and forecast density are revealed for the first time publicly.

Enhanced radiation at aviation altitudes is a concern for flight crew and passengers. During space weather events, solar flares and coronal mass ejection (CME) driven shocks are sources of energetic particles that can reach Earth's near-space environment and interact with its magnetic field and atmosphere. Although Earth's magnetic field and atmosphere offer some protection, at high aviation altitudes and particularly near the poles, this shielding effect is weaker leading to increasing radiation exposure and related health risks. In this study, we use data from the Automated Radiation Measurements for Aerospace Safety (ARMAS) instrument onboard a commercial United Airlines flight from San Francisco to Paris that deviated its flight path to mitigate the risk of increased radiation doses during the extreme geomagnetic storm in May 2024. This allows investigation of how the crew and passengers may have experienced enhanced radiation onboard the aircraft. For comparison, we estimate radiation exposure for an alternative flight from San Francisco to Paris around the same time that did not deviate from its planned path. The results show that during the 10 May 2024 geomagnetic storm, ARMAS measured sporadic high absorbed dose rates onboard the deviated flight. However, exposure could have been significantly higher (up to three times higher) if the airline had not deviated to lower latitudes, highlighting the need for precautionary measures during space weather events. Additionally, it is shown that precipitating electrons from the Van Allen radiation belts may significantly contribute to radiation levels at flight altitudes during enhanced geomagnetic activity.

Abstract Nowcasting and forecasting of the radiation environment in the Earth's lower atmosphere are critical for the safety of aircraft and spacecraft crews and passengers. Currently, this problem is addressed by employing statistical and physics‐based models that take into account particle transport and precipitation. However, given the increased number of radiation measurements available to the community, it is possible to start developing data‐driven approaches. We prepared Machine Learning‐ready (ML‐ready) data sets to nowcast the effective dose rates at aviation altitudes. The presented data sets contain 92,476 individual measurements from 589 flights obtained by the Automated Radiation Measurements for Aerospace Safety (ARMAS) experiment from 2013 to 2023. The ARMAS measurements are augmented with the properties of the Geospace environment, such as solar soft X‐ray and proton fluxes, solar wind properties, secondary cosmic ray neutrons, space weather indexes, and global solar activity indicators (such as daily sunspot number). ARMAS data are separated into three partitions, ensuring that (a) the data points from a single flight remain within the same partition, and (b) each partition samples the flight locations and Geospace environment conditions equally. Several versions of the data sets allow predictions based on point‐in‐time measurements and use up to 24 hr of Geospace parameter history. The test of the use case demonstrates a possibility of nowcasting ARMAS measurements with accuracies slightly better than the considered physics‐based models. The publicly available ML‐ready data sets could serve as the first step in data preparation for ML‐driven nowcasting and forecasting of the radiation environment.

The campaign of Automated Radiation Measurements for Aerospace Safety (ARMAS) has revealed that relativistic electron precipitation (REP) from the radiation belts can significantly enhance the radiation environment at aviation altitudes, in addition to the well-known sources of galactic cosmic rays and solar energetic particles. Recent studies using measurements from Van Allen Probes have found that ARMAS radiation doses are closely related to plasmaspheric hiss observed in the inner magnetosphere, which can scatter energetic electrons into the Earth's atmosphere. However, there still lacks a direct comparison between measurements of radiation doses and precipitating electrons. Therefore, in this statistical study, we compare measurements from ARMAS and Polar-orbiting Observational Environmental Satellites (POES). Out of more than 700 ARMAS experiments conducted between 2013 and 2019, there are 106 conjunction events, in which the POES satellite was close to ARMAS flight in both space and time. We have quantified the correlation between ARMAS-measured radiation doses and POES-measured precipitating fluxes at different electron energies. The correlation coefficient is, in general, low for precipitating electrons with energies below MeV, but becomes larger than 0.5 for electron energies above 1.89 MeV, and the largest coefficient is as high as 0.60 for 8.95-MeV precipitating electrons. The results show that ARMAS measurements are correlated with REP, indicating a potential contribution of relativistic precipitating electrons to the radiation environment at aviation altitudes.

Increased radiation levels in Earth's atmosphere can present significant risks to airline pilots, passengers, and commercial space travelers. Recent findings have revealed a strong statistical link between radiation dose rates detected at aviation altitudes (>9km) and plasmaspheric hiss wave power observed along the same magnetic field lines within the inner magnetosphere. Plasmaspheric hiss waves are crucial in depleting energetic electrons from Earth's radiation belts by causing them to precipitate into the upper atmosphere. In this study, we examine magnetic conjunction events between the Automated Radiation Measurements for Aerospace Safety (ARMAS) instruments and the Van Allen Probes to explore the relationship between plasmaspheric hiss waves and enhanced radiation at aviation altitudes. Specifically, we focus on how variations in conjunction timing, together with shifts in L-shell, and Magnetic Local Time influence the correlation between radiation dose rates and plasmaspheric hiss wave power. This investigation aims to determine whether the observed increase in radiation at aviation altitudes is directly linked to plasmaspheric hiss waves within the inner magnetosphere and to explore the extent to which enhanced radiation due to plasmaspheric hiss waves is localized in space and time. Results show that the strongest cross-correlation is only observed when plasmaspheric hiss waves and radiation doses occur nearly simultaneously and with close proximity. Spatiotemporal variations result in a degradation of the observed correlation.

Enhanced radiation in the Earth's atmosphere can pose serious hazards to pilots, aircraft passengers, and commercial space travelers. Recent results have shown, statistically, that there is a strong correlation between dose rates observed by Automated Radiation Measurements for Aerospace Safety (ARMAS) instruments at aviation altitudes (>9 km) and plasmaspheric hiss wave power measured by NASA's Van Allen Probes within the inner magnetosphere. Plasmaspheric hiss waves play a very important role in removing energetic electrons from the Earth's radiation belts by precipitating them into the upper atmosphere. These relativistic electrons generally drift eastwards along closed magnetic drift shells. In this study, we use magnetic conjunction events between ARMAS and the Van Allen Probes to analyze the causality between plasmaspheric hiss waves and enhanced radiation observed at aviation altitude. We specifically study how the size of the conjunction window and a shift in L and MLT of the conjunction window affect the correlation between dose rates and plasmaspheric hiss wave power. This is to determine if the observed enhanced radiation at aviation altitude is indeed caused by the plasmaspheric hiss waves in the inner magnetosphere. The results show that the enhanced radiation levels are only correlated with plasmaspheric hiss waves within conjunction windows of -1 <= L <= 1 and 0 <= MLT <= 2. The correlation between dose rate and hiss wave power increases slightly if ARMAS is shifted approximately 1 hr in MLT to the east of the Van Allen Probes, consistent with the drift trajectory of the electrons precipitating into the atmosphere.

Editorial for the Research Topic collection Impacts of the Extreme Gannon Geomagnetic Storm of May 2024 throughout the Magnetosphere-Ionosphere-Thermosphere System, published in Frontiers in Astronomy and Space Science.

The Liulin-SET spectrometer, developed at the Space Research and Technology Institute of the Bulgarian Academy of Sciences, was integrated with the Automated Radiation Measurements for Aerospace Safety (ARMAS) Flight Module Number 9 (FM9). The ARMAS FM9 was developed by Space Environment Technologies (SET) in Pacific Palisades, California, USA. Inclusion of the abbreviation “SET” in the name of the instrument underlined that this spectrometer was developed especially for the Space Environment Technologies (SET) ARMAS FM9 mission.ARMAS FM9 was launched on February 19, 2022 with the Northrop Grumman-Antares rocket from NASA's east coast launch facility in Virginia and operated externally on the Japanese Experimental Module of the International Space Station (ISS) for 216 days, from March to December 2022. During this period, it measured the ionizing dose and flux of three radiation components: (1) Galactic Cosmic Rays (GCR), (2) Inner Radiation Belt (IRB) energetic protons in the South Atlantic Anomaly (SAA) region, (3) Outer Radiation Belt (ORB) energetic electrons in the high-latitude regions of the ISS orbit. This paper presents the analysis of the Liulin-SET data and compares it with data from other four Liulin type instruments that worked on the ISS between 2001 and 2016.

Abstract Exposure to ionizing radiation from galactic cosmic rays (GCR) and solar energetic particles (SEP) at aircraft flight altitudes can have an adverse effect on human health. Although airline crews are classified as radiation workers by the International Commission on Radiological Protection (ICRP), in most countries, their level of exposure is unquantified and undocumented throughout the duration of their career. As such, there is a need to assess pilot ionizing radiation exposure. The Nowcast of Aerospace Ionizing RAdiation System (NAIRAS), a real‐time, global, physics‐based model is used to assess such exposure. The Automated Radiation Measurements for Aerospace Safety (ARMAS) measurement data set consists of high latitude, high altitude, and long‐duration aircraft flights between 2013 and 2023. Here, we characterize radiation exposure at aviation flight altitudes using the NAIRAS model and compare with 45 flight trajectories from the recent ARMAS flight measurement inventory.

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.

The Cassini Orbiter Ultraviolet Imaging Spectrograph (UVIS) obtained interplanetary hydrogen Ly α observations from 1999 to 2017, with mid-2004 to 2017 observations obtained from Saturn orbit. During its Saturn orbital phase, the spacecraft moved from mostly downwind and sidewind in the heliosphere to upwind. We analyze the full set of observations with our existing hot hydrogen density model with a solar illumination model most recently used to study Solar and Heliospheric Observatory Solar Wind Anisotropy Experiment data and selected Cassini UVIS observations from 2003 to 2004. We find general agreement between data and model, but with evidence for a decline in UVIS Ly α sensitivity, with a significant decline in 2002 June during a starburn event and an overall roughly linear decline in sensitivity. While earlier work by Pryor et al. fit the UVIS Ly α data from 2003 to 2004 with a hydrogen density in the outer heliosphere (but after filtration at outer heliospheric boundaries) of 0.085 cm ^−3 using the UVIS laboratory sensitivity calibration, including the sensitivity decline found here leads to a revised hydrogen density estimate of n _H = 0.14 ± 0.03 cm ^−3 . This density estimate is consistent with a recent neutral hydrogen density estimate near the termination shock of 0.127 ± 0.015 cm ^−3 based on models of observations of pick-up hydrogen ions from the New Horizons spacecraft.

The Lunar Reconnaissance Orbiter Lyman-Alpha Mapping Project (LAMP) has been mapping the Moon since its launch in 2009. Faint ultraviolet illumination of the lunar dark side includes light from stars and from hydrogen Ly alpha emissions, mostly attributed to sunlight scattered by hydrogen atoms near the Sun with a smaller contribution from the whole Galaxy. Models of the lunar illumination by time-dependent Ly alpha photons have allowed the LAMP team to map polar shadowed craters suspected of harboring water ice and other volatiles. This paper describes the model that provides daily all-sky Ly alpha maps tuned by comparisons with all-sky Ly alpha maps from the SOlar and Heliospheric Observatory Solar Wind ANisotropy Experiment stationed at the Sun-Earth L1 point.

This paper is the second part of two papers on global coordination in space weather. In this paper the activities of established and emerging international organizations and initiatives related to space weather research and operations are introduced. As shown in the accompanying paper “Global Landscape of Space Weather Observations, Research and Operations”, most of instrumentations for space environment monitoring are operated by each country. On the other hand, it is necessary to integrate the global observation to detect space weather phenomena, and it is essential to coordinate among nations for data sharing, set standard formats and protocols, fill observational gaps, etc. There are multiple international organizations and other actors in the field of space weather, and they have their own purposes and goals. In 2022, three international organizations, WMO, ISES and COSPAR reached an agreement to explore pathways to increased coordination of activities. There is also an emerging movement by various space agencies that fund space weather research missions to establish a forum to share plans and foster discussions leading to possible collaborations that advance understanding and enable progress of space weather operations and applications.

In recent years there has been a growing interest from the aviation community for space weather radiation forecasts tailored to the needs of the aviation industry. In 2019 several space weather centers began issuing advisories for the International Civil Aviation Organization alerting users to enhancements in the radiation environment at aviation flight levels. Due to a lack of routine observations, radiation modeling is required to specify the dose rates experienced by flight crew and passengers. While mature models exist, support for key observational inputs and further modeling advancements are needed. Observational inputs required from the ground-based neutron monitor network must be financially supported for research studies and operations to ensure real-time data is available for forecast operations and actionable end user decision making. An improved understanding of the geomagnetic field is required to reduce dose rate uncertainties in regions close to the open/closed geomagnetic field boundary, important for flights such as those between the continental US and Europe which operate in this region. Airborne radiation measurements, which are crucial for model validation and improvement, are lacking, particularly during solar energetic particle events. New measurement campaigns must be carried out to ensure progress and in situ atmospheric radiation measurements made available for real-time situational awareness. Furthermore, solar energetic particle forecasting must be improved to move aviation radiation nowcasts to forecasts in order to meet customer requirements for longer lead times for planning and mitigation.

White paper 2: space weather applications related to robotic and human exploration in low-Earth orbit 1 Critical needs for radiation monitoring from the surface to LEO to aid operational systems W. Kent Tobiska, Space Environment Technologies Synopsis: Air safety has improved significantly over the past decades except for effects from space weather, which includes ionizing radiation.Radiation exposure is a natural hazard faced by aircrew, high-altitude pilots, frequent flyers, and commercial space travelers to altitudes as high as the International Space Station (ISS).Their avionics can also be affected.Multiple sources of ionizing radiation contribute dose exposure in the aerospace environment that reaches from Earth's surface into space.Galactic cosmic rays (GCRs) and solar energetic particles (SEPs) are the dominant ionizing radiation sources.A third radiation source has been recently hypothesized, based on measurements, and likely originates from the wave-particle interaction in the Van Allen radiation belts (RB) leading to precipitated charged particles (PCPs).Mature measurement capabilities exist for providing radiation detection, including the Automated Radiation Measurements for Aerospace Safety (ARMAS) system.ARMAS is a decade-long national capacity-building, science-driven technology demonstration program providing a pathway for cost-effective identification and management of radiation risks created by space weather.The ARMAS program serves four use-cases that have forecasted growth: i) subsonic commercial aviation; ii) subsonic business jet aviation; iii) supersonic or high-altitude aviation; and iv) commercial spaceflight.The conclusion from the AR-MAS program is that a new, dedicated vehicle needs to be built for continuous radiation monitoring.Such a vehicle would host instruments for providing 24/7, real-time monitoring of the radiation environment with data processing on the ground, distribution to archives, and an instant-access apps.

Today we see an expanding drive for global, high-speed internet, which is the de-facto life blood of the global economy and of our national defense.The demand for higher internet speeds with global internet connectivity, anywhere, anytime, touches every part of our technological society.Commercial efforts, such as SpaceX's Starlink constellation, but not limited to them, are now hugely expanding global internet capacity in the next two years.With more constellations planned, the number of LEO objects is set to TRIPLE in two years.The growth in the number of LEO objects directly increases the probability of unintentional collisions between objects due to accumulating space debris.This is called the runaway Kessler syndrome, where more and more unavoidable collisions occur and leads to a potentially unusable LEO orbital domain.There are three ways to reduce the risks associated with debris are: 1) limit the generation of new debris; 2) better track and characterize debris; 3) and remediate debris that have already been created.The recommendations for the community's efforts include both technical and scientific activities, using both research to operations and operations to research foci.Those recommendations identify ways to create an operationally viable uncertainty solution for the global thermosphere across all altitudes and time frames, methods to remediate the small size debris in LEO, and physical processes that must be better understood to improve the uncertainty solution of the global thermosphere across all altitudes and time frames.

Abstract It is believed that galactic cosmic rays and solar energetic particles are the two major sources of ionizing radiation. However, the radiation source may also be due to relativistic electrons that are associated with precipitation from the Van Allen radiation belts. In this study, we use Automated Radiation Measurements for Aerospace Safety (ARMAS) measurements to investigate the precipitation mechanism of energetic radiation belt electrons. ARMAS instruments are flown on agency‐sponsored (NASA, National Oceanic and Atmospheric Administration, National Science Foundation, Federal Aviation Administration, DOE) flights, commercial space transportation companies and airliners (>9 km) in automated radiation collection mode. We identified magnetic conjunction events between ARMAS and NASA's Van Allen Probes to study the highly variable, dynamic mesoscale radiation events observed by ARMAS instruments at aviation altitudes and their relationship to various plasma waves in the inner magnetosphere measured by the Van Allen Probes. The results show that there is a strong correlation between dose rates observed by ARMAS and plasmaspheric hiss wave power measured by the Van Allen Probes, but no such relationship with electromagnetic ion cyclotron waves and only a modest correlation with whistler mode chorus waves. These results suggest that the space environment could have a potentially significant effect on passenger safety.