We present data from the sister instruments Merlin and cosmic radiation environment dosimetry and charging experiment (CREDANCE), from medium Earth orbit (MEO) and the slot region, respectively. Each instrument measures internal charging current, proton and ion flux, and total ionizing dose with an identical suite of instruments. In this article, we present charging current and proton flux data. Merlin flew on board the Giove-A MEO testbed spacecraft from December 2005 to November 2021. CREDANCE flew on board the Demonstration and Science Experiments (DSX) spacecraft from July 2019 to May 2021.

Within the next decade it is likely that the space tourism industry will grow dramatically and the number of humans travelling into, and beyond, the stratosphere via commercial entities such as World View and Space Perspective will increase. Current space tourism ventures focus on long duration very high altitude balloon flights; also known as 'near space' flights, sub-orbital flights and visits to Low Earth Orbit (LEO). In the next few decades space tourism is ultimately likely to become routine. During these new commercial ventures the effects of cosmic radiation exposure, especially during sudden changes in space weather, such as ground level enhancement (GLE) events, could have significant health implications for crew and passengers. The risks from these rapid changes in space weather and potential radiation exposure during flights is not currently fully understood or even acknowledged. Legislation and regulation for such enterprises is also in its infancy with little or no guidance for commercial entities or potential passengers. Initial work at the University of Surrey has focused on very high altitude 'near space' balloon flights. World-wide launch locations for flights have been modelled using MAIRE and CARI-7 computer programs. Flight routes have been monitored, for current commercial and higher flight levels, using the Smart Atmospheric Ionizing Radiation (SAIRA) detector. The modelled flight profiles have been compared with detector data, up to a maximum flight altitude of 30 km (10 0,0 0 0 ft), with varying space weather conditions, from norms to extreme events, to assess the radiation risk presented by potential exposure.Plain Language Summary: An assessment of the risks and potential radiation exposure from flying to 'near space' within newly designed observation balloons at very high altitude in the upper atmosphere above the Earth. Looking at the impact of radiation from the sun and sources outside the solar system, and critically when these conditions vary which could result in high levels of exposure.(c) 2023 International Association for the Advancement of Space Safety. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )

The objectives, instrumentation, methods, and data leading up to launch of the NASA Living With a Star (LWS) Space Environment Testbed (SET) payload onboard the Air Force Research Laboratory Demonstration and Science Experiments (DSX) spacecraft are described. The experiments characterize the space radiation environment and how it affects the hardware performance. The payload consists of a compact space weather instrument and a carrier containing four board experiments.

Abstract Significant increases to the atmospheric radiation environment are recorded by a network of ground level neutron monitors as ground level enhancements (GLEs). These space weather phenomena pose a risk to aviation via single event effects in aircraft electronics and ionizing dose to passengers and crew. Under the UK Space Weather Instrumentation, Measurement, Modeling and Risk programme, we have developed a new model to provide nowcasts of the aviation radiation environment, including both the galactic cosmic ray (GCR) background and during GLE events. The Model for Atmospheric Ionising Radiation Effects (MAIRE+) uses multiple data sources to characterize primary GCR and GLE particle spectra and combines these with precalculated geomagnetic and atmospheric response matrices to predict particle fluxes from ground level to 20 km altitude across the entire globe. Two European neutron monitors (located at Oulu in Finland and Dourbes in Belgium) are used as the primary indicators of GLE intensity in order to maximize accuracy over UK airspace. Outputs from MAIRE+ for the historical GLEs in September and October 1989 are compared to recalibrated empirical data from a solid‐state detector that was carried on Concorde in that period. The model will be hosted in the UK and will provide additional capability to the Met Office Space Weather Operations Center (MOSWOC).

Abstract Ground level enhancements (GLEs) are space weather events that pose a potential hazard to the aviation environment through single event effects in avionics and increased dose to passengers and crew. The existing ground level neutron monitoring network provides continuous and well‐characterized measurements of the radiation environment. However, there are only a few dozen active stations worldwide, and there has not been a UK‐based station for several decades. Much smaller neutron detectors are increasingly deployed throughout the world with the purpose of using secondary neutrons from cosmic rays to monitor local soil moisture conditions (COSMOS). Space weather signals from GLEs and Forbush decreases have been identified in COSMOS data. Monte Carlo simulations of atmospheric radiation propagation show that a single COSMOS detector is sufficient to detect the signal of a medium‐strength (10%–100% increase above background) GLE at high statistical significance, including at fine temporal resolution. Use of fine temporal resolution would also provide a capability to detect Terrestrial Gamma Ray Flashes (via secondary neutrons) which are produced by certain lightning discharges and which can provide a hazard to aircraft, particularly in tropical regions. We also show how the COsmic‐ray Soil Moisture Observing System‐UK detector network could be used to provide warnings at the International Civil Aviation Organization “Moderate” and “Severe” dose rate thresholds at aviation altitudes, and how multiple‐detector hubs situated at strategic UK locations could detect a small GLE at high statistical significance and infer crucial information on the nature of the primary spectrum.

Historically, gathering data on atmospheric radiation levels during solar particle events has been difficult, as there is little or no time warning of events. Being able to accurately quantify radiation levels within the atmosphere during solar events is of significance to the aviation industry, as described in the International Civil Aviation Organization's (ICAO) Space Weather manual. Particularly during a large ground-level enhancement (GLE) where the ionizing dose to passengers and crew can exceed the recommended general public annual dose limits, set by the International Commission for Radiological Protection (Barlett, Beck, Bilski, Bottollier-Depois, & Lindborg, 2004, https:// doi.org/10.1093/rpd/nch232), in a single flight. The Smart Atmospheric Ionizing RAdiation (SAIRA) Monitoring Network is a new system of handheld radiation detectors that can be carried on aircraft to monitor and record atmospheric radiation levels. The system operates via citizen science volunteers, who record radiation data as they travel for normal purposes. Over 30 flights have been conducted with volunteers to demonstrate that a citizen science network is possible. Volunteers have used a new Android application to record and upload data to a central server to form a database of flight measurements. The demonstration has shown that there is a willingness in public volunteers to use radiation detectors and engage in science outreach. A fully developed system will ideally provide the capability to quantify radiation levels during a solar particle event or ground-level enhancement and the data can be used by relevant organizations to minimize potential risks.

We use electron flux derived from the environment monitoring unit "(EMU)-SURF" current monitor on board a Galileo Global Navigation Satellite System (GNSS) constellation satellite to modify and update the model of outer belt electrons for dielectric internal charging (MOBE-DIC). We describe how this data set, together with data from similar current-measuring instruments on Van Allen Probes, Giove-A, and STRV1d, are used to improve and expand the model. We have extended the spatial range to include the inner belt, exploited EMU data to widen the energy range for the electron spectrum, updated the statistical analysis of flux variation using a data set double the size used for the original model, and established a new and independent latitude function that yields improved agreement in medium earth orbit compared to the original model. The model is entirely characterized by a set of equations and parameters that produce fluxes as a function of magnetic coordinates at three distinct statistical levels.

The radiation environment of the Galileo spacecraft is severe and poorly characterized. The Galileo orbit takes the spacecraft through the heart of the outer radiation belt, while the low levels of geomagnetic shielding throughout the orbit expose the spacecraft to intermittent intense fluxes of protons during solar energetic particle events. In the Galileo constellation, two environmental monitoring units (EMUs) are currently flying in two different orbital planes. These units monitor the radiation environment and provide critical information related to hazards for the host spacecraft and its payload. In this paper, we present the results from the analysis of the surface charge collecting plates and the proton telescope sensors. The performed numerical calibration of the EMU sensors and the application of novel unfolding and in-flight cross-calibration techniques allow the calculation of high-quality proton and electron differential fluxes. The creation of a high-quality, long-term EMU electron flux data set, is a step forward toward the improved characterization of medium earth orbit (MEO) environment through the update of the existing or the development of new radiation environment models.

High‐energy trapped electrons in the Van Allen belts pose a threat to the survivability of orbiting spacecraft. Two key radiation effects are total ionizing dose and displacement damage dose in components and materials, both of which cause cumulative and largely irreversible damage. During an extreme space weather event, trapped electron fluxes in the Van Allen belts can increase by several orders of magnitude in intensity, leading to an enhanced risk of satellite failure. We use extreme environments generated by modeling and statistical analyses to estimate the consequences for satellites in terms of the radiation effects described above. A worst‐case event could lead to significant losses in power generating capability—up to almost 8%—and cause up to four years' worth of ionizing dose degradation, leading to component damage and a life‐shortening effect on satellites. The consequences of such losses are hugely significant given our increasing reliance on satellites for a vast array of services, including communication, navigation, defense, and critical infrastructure.

Solar energetic particle events create radiation risks for aircraft, notably single-event effects in microelectronics along with increased dose to crew and passengers. In response to this, some airlines modify their flight routes after automatic alerts are issued. At present these alerts are based on proton flux measurements from instruments onboard satellites, so it is important that contemporary atmospheric radiation measurements are made and compared. This paper presents the development of a rapid-response system built around the use of radiosondes equipped with a radiation detector, Zenith, which can be launched from a Met Office weather station after significant solar proton level alerts are issued. Zenith is a compact, battery-powered solid-state radiation monitor designed to be connected to a Vaisala RS-92 radiosonde, which transmits all data to a ground station as it ascends to an altitude of similar to 33 km. Zenith can also be operated as a stand-alone detector when connected to a laptop, providing real-time count rates. It can also be adapted for use on unmanned aerial vehicles. Zenith has been flown on the Met Office Civil Contingency Aircraft, taken to the European Organization for Nuclear Research-EU high energy Reference Field facility for calibration and launched on a meteorological balloon at the Met Office's weather station in Camborne, Cornwall, UK. During this sounding, Zenith measured the Pfotzer-Regener maximum to be at an altitude of 18-20 km where the count rate was measured to be 1.15 c s(-1) cm(-2) compared to 0.02 c s(-1) cm(-2) at ground level.

The NASA Radiation Dosimetry Experiment (RaD-X) successfully deployed four radiation detectors on a high-altitude balloon for a period of approximately 20 h. One of these detectors was the RaySure in-flight monitor, which is a solid-state instrument designed to measure ionizing dose rates to aircrew and passengers. Data from RaySure on RaD-X show absorbed dose rates rising steadily as a function of altitude up to a peak at approximately 60,000 feet, known as the Pfotzer-Regener maximum. Above this altitude absorbed dose rates level off before showing a small decline as the RaD-X balloon approaches its maximum altitude of around 125,000 feet. The picture for biological dose equivalent, however, is very different. At high altitudes the fraction of dose from highly ionizing particles increases significantly. Dose from these particles causes a disproportionate amount of biological damage compared to dose from more lightly ionizing particles, and this is reflected in the quality factors used to calculate the dose equivalent quantity. By calculating dose equivalent from RaySure data, using coefficients derived from previous calibrations, we show that there is no peak in the dose equivalent rate at the Pfotzer-Regener maximum. Instead, the dose equivalent rate keeps increasing with altitude as the influence of dose from primary cosmic rays becomes increasingly important. This result has implications for high altitude aviation, space tourism and, due to its thinner atmosphere, the surface radiation environment on Mars.

Results are presented from evaluations of radiation dosimeters prior to a NASA high-altitude balloon flight, the RaD-X mission. Four radiation dosimeters were on board RaD-X: a Far West Hawk (version 3), a Teledyne dosimeter (UDOS001), a Liulin dosimeter (MDU 6SA1), and a RaySure dosimeter (version 3b). The Hawk is a tissue-equivalent proportional counter (TEPC) and the others are solid-state Si sensors. The Hawk served as the flight standard and was calibrated for this mission. The Si-based dosimeters were tested to make sure they functioned properly prior to flight but were not calibrated for the radiation environment in the stratosphere. The dosimeters were exposed to Co-60 gamma rays and Cf-252 fission radiation (which includes both neutrons and gamma rays) at the Lawrence Livermore National Laboratory (LLNL). The measurement results were compared with results from standard benchmark measurements of the same sources and source-to-detector distances performed contemporaneously by LLNL calibration facility personnel. For Co-60 gamma rays, the dosimeter-to-benchmark ratios were 0.840.06, 1.070.32, 1.310.07, and 0.820.24 for the TEPC, Teledyne, Liulin, and RaySure, respectively. For Cf-252 radiation, the dosimeter-to-benchmark ratios were 0.94 +/- 0.15, 0.55 +/- 0.18, 0.58 +/- 0.08, and 0.33 +/- 0.12 for the TEPC, Teledyne, Liulin, and RaySure. Some examples of how the results were used to help interpret the flight data are also presented.

The design, development and first flight results of the MuREM and prototype SSTL-RM miniaturised radiation monitors, capable of measuring the space radiation environment and its effects on electronics, are presented, leading to the deployment of standardised monitors for commercial spacecraft.

The SURF internal charging monitor that measures deposited currents in three shielded aluminum plates is one of the sensors within the Merlin radiation monitoring instrument launched on Giove-A in December 2005 into a 23300-km circular 56° inclination medium earth orbit. The instrument has now completed 8.5 years in orbit despite being originally intended for a two-year operational life. Here, we report on the instrument's health, provide further recent data, and review the overall results in terms of their engineering significance. It is concluded that the instrument remains in good health, with no significant deterioration, and a near continuous data set from December 2005 to April 2014 is now available. The maximum plate currents to date were recorded over the period April 6-8, 2010, during a significant outer electron belt enhancement (also observed by Geostationary Operational Environmental Satellite (GOES)-12 in geostationary orbit), which persisted for several days. From April 7 to April 9, 2010, the current in the most shielded plate (1.0-mm thickness with 1.5-mm shielding) exceeded the widely used 0.1-pA cm -2 safety threshold for internal charging (the only days in the mission where this occurred), and on these days, it also exceeded the reasonable worst case current predications given by the DICTAT internal charging tool (the other plate currents remained within DICTAT predictions). The 0.02-pA cm -2 safety threshold used in European ECSS charging standards for dielectrics below 25 °C has been exceeded on a far larger number of days; for example, in the most shielded plate, it has been exceeded on 55 days (8% of the total).

There has been considerable research on measurements and simulation of the cosmic radiation doses for aircrew. Most of this was made in the northern hemisphere and on routes between Europe, Asia and North America. The current work shows the results of measurements made onboard a military aircraft specifically in the South Atlantic Anomaly Region, comparing some active and passive instruments and the results from computational dose estimation with special concern about possible effects from the anomaly on the radiation doses.

In this work we present the development of the electron Slot Region Radiation Environment Model (e-SRREM). e-SRREM is a data-based statistical model that describes the trapped electron fluxes in the slot region between the inner and the outer electron radiation belts. For a user-defined mission orbit and duration, the model provides energetic electron fluxes determined by confidence levels.

With the development of next generation aircraft designs capable of ultralong-range flight and extended flight endurance, new experimental dosimetry equipment has been specifically designed to enable aircrew to monitor and respond to airborne alerts of potential doses that exceed recommended limits. The new QinetiQ QDOS/Rayhound monitor and designer-specific Liulin 4SA both provide real-time monitoring and readout with both audible and visual alert functions. The potential advantage to pilots and airlines is a more rational response to an alert by minimizing the altitude descent and time at lower levels in response to a significant event. This not only protects passengers and crew from solar particle events but provides a "greener'' option to fuel burn at lower altitudes when events have abated. Thus, it will allow the crew to determine safer optimum flight levels during and after the event. These monitors were flown on numerous high-and low-latitude flights in combination with a "Hawk'' tissue equivalent proportional counter acting as the reference instrument as it measured the total ambient dose equivalent H*(10). An FH 41B Eberline monitor and bubble detectors were also used in the comparison.

The assessment of the exposure to cosmic radiation onboard aircraft is one of the preoccupations of bodies responsible for radiation protection. Cosmic particle flux is significantly higher onboard aircraft than at ground level and its intensity depends on the solar activity. The dose is usually estimated using codes validated by the experimental data. In this paper, a comparison of various codes is presented, some of them are used routinely, to assess the dose received by the aircraft crew caused by the galactic cosmic radiation. Results are provided for periods close to solar maximum and minimum and for selected flights covering major commercial routes in the world. The overall agreement between the codes, particularly for those routinely used for aircraft crew dosimetry, was better than +/- 20 % from the median in all but two cases. The agreement within the codes is considered to be fully satisfactory for radiation protection purposes.

Radiation exposure of aircraft crew caused by cosmic radiation is regulated in Europe by the European Community Council Directive 96/29/EURATOM and implemented into law in almost every country of the European Union. While the galactic cosmic radiation (GCR) leads on average to an exposure of about 3 mSv per year, solar cosmic radiation can lead to 1 mSv per one subsonic flight during solar storm periods. Compared to GCR, solar cosmic radiation shows a much softer proton spectrum but with a larger contribution of several orders of magnitude. This is the reason for the large radiation exposure in high northern and southern geographic latitudes during solar particle events. Here an overview of active radiation in-flight measurements undertaken during solar storms is given. In particular, tissue-equivalent proportional counter on-board measurements are shown and the radiation quality during solar storm periods with that for GCR is compared.

Electron environment specification models have been developed to assess long term effects (e.g. doses) as well as short term effects (e.g. internal charging) for navigation orbiting spacecraft design.