Keith Ryden

Dr Keith Ryden


Reader in Space Engineering
PhD MSc BSc(Hons) CEng FIET
+44 (0)1483 682226
22 BA 01

Biography

Areas of specialism

Space Environment; Radiation Effects

Research

Research interests

My publications

Publications

Hands A, Morris P, Ryden K, Dyer C, Truscott P, Chugg A, Parker S (2011) Single event effects in power MOSFETs due to atmospheric and thermal neutrons, IEEE Transactions on Nuclear Science 58 (6) pp. 2687-2694 IEEE
Eight commercially available n-channel power MOSFETs were exposed to high energy spallation neutrons and thermal neutrons in separate experiments. Single event burnout (SEB) was observed in several of the devices in both environments. Measurements of SEB at derated drain-source voltages show very strong reductions in burnout cross-sections, but suggest that current recommendations for safe operation of devices may need updating for high voltage devices. In one device a different failure mode was observed, with subsequent investigations suggesting that single event gate rupture (SEGR) was responsible. This first observation of SEGR in accelerated neutron testing of power MOSFETs represents a new consideration for designers of high voltage control systems. © 2011 IEEE.
Hands A, Ryden K, Underwood C, Rodgers D, Evans H (2015) A New Model of Outer Belt Electrons for Dielectric Internal Charging (MOBE-DIC), IEEE TRANSACTIONS ON NUCLEAR SCIENCE 62 (6) pp. 2767-2775 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Ryden KA, Hands ADP, Underwood CI, Rodgers DJ (2015) Internal Charging Measurements in Medium Earth Orbit Using the SURF Sensor: 2005-2014, IEEE TRANSACTIONS ON PLASMA SCIENCE 43 (9) pp. 3014-3020 IEEE
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 23,300-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).
Bourdarie S, Lazaro D, Hands A, Ryden K, Nieminen P (2009) Electron environment specification models for navigation orbits, Proceedings of the European Conference on Radiation and its Effects on Components and Systems, RADECS pp. 364-368
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. © 2009 IEEE.
Rodgers D, Evans H, Underwood C, Taylor B, Ryden K, Mandorlo G, Daly E (2008) Lessons learned on Galileo radiation environment from GIOVE, International Astronautical Federation - 59th International Astronautical Congress 2008, IAC 2008 13 pp. 8277-8281
The GIOVE satellites (A, B) are test satellites for the European Galileo constellation. It is recognised that the Galileo orbital radiation environment is particularly severe and therefore these satellites carry environment monitoring equipment. This contribution will present some of the observations made and discuss what they teach us about the environment expected for the final Galileo constellation.
Hands A, Morris P, Ryden K, Dyer C (2012) Large-scale multiple cell upsets in 90 nm commercial SRAMs during neutron irradiation, IEEE Transactions on Nuclear Science 59 (6) pp. 2824-2830
During neutron irradiation of 4-Mb SRAMs, large-scale multiple cell upsets (MCUs) were observed. These were observed in 90-nm devices at accelerated test facilities providing fission, fusion, and spallation neutron environments. The MCUs are shown to manifest themselves in 2-D patterns encompassing scores of cells, which, even with bit interleaving, lead to uncorrectable multiple bit upsets (MBU) in the same word. The mechanism behind the MCU appears to be micro-latching within blocks of the memory array that are powered up sequentially during the read cycle of the device. © 1963-2012 IEEE.
Taylor B, Underwood CI, Evans HDR, Ryden K, Rodgers D, Daly EJ, Mandorlo G, Falcone M, Morris PA, Prieto RG (2007) Results from the Galileo Giove - A radiation monitors and comparison with existing radiation belt models, IEEE Transactions on Nuclear Science 54 (4) pp. 1076-1081
The radiation monitors on board the Galileo Giove-A satellite, CEDEX and Merlin, and their data are presented. The instruments include energetic proton and ion detectors, an internal charging monitor, RADFETs and experimental dose-rate photodiodes. A comparison of the data with existing monitors and models is presented. © 2007 IEEE.
Ryden Keith, Morris PA, Ford KA, Hands ADP, Dyer CS, Taylor B, Underwood Craig, Rodgers DJ, Mandorlo G, Gatti G, Evans HDR, Daly EJ (2008) Observations of Internal Charging Currents in Medium Earth Orbit, IEEE TRANSACTIONS ON PLASMA SCIENCE 36 (5) pp. 2473-2481 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Ryden KA, Morris PA, Ford KA, Dyer CS, Hands A, Taylor B, Underwood CI, Rodgers DJ, Mandorlo G, Gatti G, Evans HD, Daly EJ (2007) Observations of internal charging and outer-belt electron enhancements from Giove-A, Proceedings of the European Conference on Radiation and its Effects on Components and Systems, RADECS
The planned Galileo global navigation system will employ an array of satellites in medium Earth orbit. Internal charging is one of the primary hazards for any spacecraft in MEO and accordingly the Galileo test spacecraft, Giove-A, carries the 'SURF' detector to undertake measurements of internal charging currents deposited at three different shielding depths (0.5, 1.0 and 1.5 mm AI). Giove-A was successfully launched on 28th December 2005 into a 23,300 km circular, 56 degree inclination orbit. In this paper we provide data on the charging currents observed in 2006, with particular emphasis on two large charging events, one in April and one in December. Comparisons are made between the flight data and predictions made using ESA's internal charging tool, DICTAT, which employs the FLUMIC 'worst case' electron belt model. The DICTAT predictions of charging current are exceeded for a few days in the 1.5mm AI shielded plate in the course of the December event. © 2007 IEEE. © 2007 IEEE.
Taylor B, Underwood Craig, Evans HDR, Ryden Keith, Rodgers D, Daly EJ, Mandorlo G, Falcone M, Morris PA, Prieto RG (2007) Results from the Galileo giove - A radiation monitors and comparison with existing radiation belt models, IEEE TRANSACTIONS ON NUCLEAR SCIENCE 54 (4) pp. 1076-1081 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
The radiation monitors on board the Galileo Giove-A satellite, CEDEX and Merlin, and their data are presented. The instruments include energetic proton and ion detectors, an internal charging monitor, RADFETs and experimental dose-rate photodiodes. A comparison of the data with existing monitors and models is presented.
Tobiska WK, Atwell W, Beck P, Benton E, Copeland K, Dyer C, Gersey B, Getley I, Hands A, Holland M, Hong S, Hwang J, Jones B, Malone K, Meier MM, Mertens C, Phillips T, Ryden K, Schwadron N, Wender SA, Wilkins R, Xapsos MA (2015) Advances in Atmospheric Radiation Measurements and Modeling Needed to Improve Air Safety, Space Weather
© 2015 American Geophysical Union.Air safety is tied to the phenomenon of ionizing radiation from space weather, primarily from galactic cosmic rays but also from solar energetic particles. A global framework for addressing radiation issues in this environment has been constructed, but more must be done at international and national levels. Health consequences from atmospheric radiation exposure are likely to exist. In addition, severe solar radiation events may cause economic consequences in the international aviation community due to exposure limits being reached by some crew members. Impacts from a radiation environment upon avionics from high-energy particles and low-energy, thermalized neutrons are now recognized as an area of active interest. A broad community recognizes that there are a number of mitigation paths that can be taken relative to the human tissue and avionics exposure risks. These include developing active monitoring and measurement programs as well as improving scientific modeling capabilities that can eventually be turned into operations. A number of roadblocks to risk mitigation still exist, such as effective pilot training programs as well as monitoring, measuring, and regulatory measures. An active international effort toward observing the weather of atmospheric radiation must occur to make progress in mitigating radiation exposure risks. Stakeholders in this process include standard-making bodies, scientific organizations, regulatory organizations, air traffic management systems, aircraft owners and operators, pilots and crew, and even the public.
Dyer C, Hands A, Lei F, Truscott P, Ryden KA, Morris P, Getley I, Bennett L, Bennett B, Lewis B (2009) Advances in measuring and modeling the atmospheric radiation environment, IEEE Transactions on Nuclear Science 56 (6) pp. 3415-3422
New radiation monitors based on solid-state detectors have been developed to perform wide-ranging measurements of the atmospheric environment and provide warnings of sudden increases during solar particle events. Results have been obtained during the current deep solar minimum across the full range of latitudes and from sea level to 13 km altitude. Results for ambient dose equivalent agree very closely with Tissue Equivalent Proportional Counters carried on the same flights. Values of 10 ¼Sv/hr are being reached at 12 km altitude and high latitude. Comparisons are made with the QinetiQ Atmospheric Radiation Model and the need to include cosmic-ray heavy ions is demonstrated. © 2009 IEEE.
Taylor B, Underwood CI, Ryden KA, Morris PA (2009) A GIOVE Derived Galileo Electron Spectrum and Comparison to Models, IEEE TRANSACTIONS ON NUCLEAR SCIENCE 56 (6) pp. 3423-3428 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Tobiska WK, Atwell W, Beck P, Benton E, Copeland K, Dyer C, Gersey B, Getley I, Hands A, Holland M, Hong S, Hwang J, Jones B, Malone K, Meier MM, Mertens C, Phillips T, Ryden K, Schwadron N, Wender SA, Wilkins R, Xapsos MA (2015) Advances in atmospheric radiation measurements and modeling needed to improve air safety, Space Weather 13 (4) pp. 202-210
©2015. American Geophysical Union. All Rights Reserved.Air safety is tied to the phenomenon of ionizing radiation from space weather, primarily from galactic cosmic rays but also from solar energetic particles. A global framework for addressing radiation issues in this environment has been constructed, but more must be done at international and national levels. Health consequences from atmospheric radiation exposure are likely to exist. In addition, severe solar radiation events may cause economic consequences in the international aviation community due to exposure limits being reached by some crew members. Impacts from a radiation environment upon avionics from high-energy particles and low-energy, thermalized neutrons are now recognized as an area of active interest. A broad community recognizes that there are a number of mitigation paths that can be taken relative to the human tissue and avionics exposure risks. These include developing active monitoring and measurement programs as well as improving scientific modeling capabilities that can eventually be turned into operations. A number of roadblocks to risk mitigation still exist, such as effective pilot training programs as well as monitoring, measuring, and regulatory measures. An active international effort toward observing the weather of atmospheric radiation must occur to make progress in mitigating radiation exposure risks. Stakeholders in this process include standard-making bodies, scientific organizations, regulatory organizations, air traffic management systems, aircraft owners and operators, pilots and crew, and even the public.
Ryden KA, Morris PA, Rodgers DJ, Dyer CS, Underwood CI, Taylor B, Jason S, Evans HD, Daley EJ, Mandorlo G, Gatti G (2006) Initial radiation measurements from Europe's Galileo test-bed satellite, GIOVE-A, AIAA 57th International Astronautical Congress, IAC 2006 4 pp. 2775-2782
In preparation for deployment of the Galileo satellite navigation system, Europe has launched a test satellite, Giove-A. One of its objectives is to measure the radiation environment encountered in medium Earth orbit (MEO) which is a new regime for European missions. Giove-A therefore includes two radiation environment monitors: Merlin supplied by QinetiQ and CEDEX supplied by the University of Surrey. Merlin measures electrostatic charging and electron fluxes, total ionising dose, energetic proton fluxes and heavy ion linear energy transfer (LET) spectra. CEDEX monitors energetic proton fluxes, heavy ion linear energy transfer (LET) spectra and ionising dose rates. Giove-A, which was built by SSTL (UK), was successfully launched on 28th December 2005 into a 23,600 km circular, 56 degree inclination orbit. Data received since launch has been analysed and demonstrates that the MEO environment is highly dynamic due to the influence of space weather. Numerous electron belt enhancement events have been observed and the charging effects of these events been characterised. Total ionising dose is also seen to be delivered almost wholly during electron events.
Hands A, Morris P, Dyer C, Ryden K, Truscott P (2011) Single event effects in power MOSFETs and SRAMs due to 3 MeV, 14 MeV and fission neutrons, IEEE Transactions on Nuclear Science 58 (3) pp. 952-959
Various SRAM and MOSFET devices were exposed to 3 MeV and 14 MeV neutrons at a fusion facility and to a fission neutron spectrum with a californium-252 source. Single event burnout (SEB) was observed in several of the MOSFETs in all three environmentsthe first time this phenomenon has been observed at neutron energies below 10 MeV. In addition to observing single event upsets (SEU) and single event latchup (SEL) in the SRAMs, two devices experienced significant multiple cell upset (MCU) effects which dominated the upset rate. The physical mechanisms underlying these phenomena and the consequences for various radiation environments are discussed. © 2011 IEEE.
Meredith NP, Horne RB, Isles JD, Ryden KA, Hands ADP, Heynderickx D (2016) Extreme internal charging currents in medium Earth orbit: Analysis of SURF plate currents on Giove-A, Space Weather 14 American Geophysical Union
Relativistic electrons can penetrate spacecraft shielding and can damage satellite components. Spacecraft in medium Earth orbit pass through the heart of the outer radiation belt and may be exposed to large fluxes of relativistic electrons, particularly during extreme space weather events. In this study we perform an extreme value analysis of the daily average internal charging currents at three different shielding depths in medium Earth orbit as a function of L? and along the orbit path. We use data from the SURF instrument on board the European Space Agency's Giove-A spacecraft from December 2005 to January 2016. The top, middle, and bottom plates of this instrument respond to electrons with energies >500 keV, >700 keV, and >1.1 MeV, respectively. The 1 in 10 year daily average top plate current decreases with increasing L? ranging from 1.0 pA cm?2 at L?=4.75 to 0.03 pA cm?2 at L?=7.0. The 1 in 100 year daily average top plate current is a factor of 1.2 to 1.8 larger than the corresponding 1 in 10 year current. The 1 in 10 year daily average middle and bottom plate currents also decrease with increasing L? ranging from 0.4 pA cm?2 at L?=4.75 to 0.01 pA cm?2 at L?=7.0. The 1 in 100 year daily average middle and bottom plate currents are a factor of 1.2 to 2.7 larger than the corresponding 1 in 10 year currents. Averaged along the orbit path the 1 in 10 year daily average top, middle, and bottom plate currents are 0.22, 0.094, and 0.094 pA cm?2, respectively.
Taylor B, Underwood C, Evans HDR, Daly E, Ryden KA, Santin G (2008) Galileo GIOVE-A MEORAD Results and Analysis, IEEE TRANSACTIONS ON NUCLEAR SCIENCE 55 (6) pp. 3151-3157 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Ryden KA, Hands A (2017) Modelling of electric fields inside spacecraft dielectrics using in-orbit charging current data, IEEE Transactions on Plasma Science 45 (5) IEEE
Internal charging caused by energetic electrons is a recognized threat to critical space infrastructure such as navigation and communication satellites. In this paper the electric field developed inside selected on-board dielectrics over a 10-year period in a GPS-like orbit is modelled using actual charging currents measured directly in orbit. The charging currents provide both charge deposition and dose rate inputs to the model, the latter allowing the introduction of radiation induced conductivity (RIC) to improve realism. As expected we find that RIC is a mitigating factor for the electric fields but they can still become very large e.g. a 1.0 mm thickness of PEEK under 0.5mm of Al shielding would be at risk of breakdown almost throughout the mission. We also find that RIC tends to reduce sensitivity to space weather perturbations of the environment such as the April 2010 storm event. This seems physically reasonable but we also know that some satellite anomalies do correlate quite well with space weather and short term (daily) electron fluence increases. We recommend that correlation of anomaly data sets with electric field models of this type is undertaken in future: this will require accurate materials parameters and also needs to take account of sudden depletion of the electric field due to discharges. In addition more charging current sensors with greater shielding levels (>2mm Al equivalent) should be flown to allow modeling of a wider range of realistic cases, including inside well-shielded electronic boxes.
Mertens CJ, Gronoff GP, Norman RB, Hayes BM, Lusby TC, Straume T, Kent Tobiska W, Hands A, Ryden KA, Benton E, Wiley S, Gersey B, Wilkins R, Xu X (2016) Cosmic Radiation Dose Measurements from the RaD-X Flight Campaign, Space Weather 14 (10) pp. 874-898
Abstract The NASA Radiation Dosimetry Experiment (RaD-X) stratospheric balloon flight mission obtained measurements for improving the understanding of cosmic radiation transport in the atmosphere and human exposure to this ionizing radiation field in the aircraft environment. The value of dosimetric measurements from the balloon platform is that they can be used to characterize cosmic ray primaries, the ultimate source of aviation radiation exposure. In addition, radiation detectors were flown to assess their potential application to long-term, continuous monitoring of the aircraft radiation environment. The RaD-X balloon was successfully launched from Fort Sumner, New Mexico (34.5°N, 104.2°W) on 25 September 2015. Over 18 hours of flight data were obtained from each of the four different science instruments at altitudes above 20 km. The RaD-X balloon flight was supplemented by contemporaneous aircraft measurements. Flight-averaged dosimetric quantities are reported at seven altitudes to provide benchmark measurements for improving aviation radiation models. The altitude range of the flight data extends from commercial aircraft altitudes to above the Pfotzer maximum where the dosimetric quantities are influenced by cosmic ray primaries. The RaD-X balloon flight observed an absence of the Pfotzer maximum in the measurements of dose equivalent rate.
Hands A, Ryden KA, Mertens C (2016) The Disappearance of the Pfotzer-Regener Maximum in Dose Equivalent Measurements in the Stratosphere, Space Weather 14 (10) pp. 776-785 American Geophysical Union
The NASA Radiation Dosimetry Experiment (RaD-X) successfully deployed four radiation detectors on a high altitude balloon for a period of approximately twenty hours. One of these detectors was the RaySure in-flight monitor, which is a solid-state instrument designed to measure ionizing dose rates to air crew 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
Hands A, Lei F, Ryden KA, Dyer C, Underwood CI, Mertens C (2016) New Data and Modelling for Single Event Effects in the Stratospheric Radiation Environment, IEEE Transactions on Nuclear Science 64 (1) pp. 587-595 IEEE
The upper atmosphere is a transition region between the neutron-dominated aviation environment and satellite environment where primary protons and ions dominate. We report high altitude balloon measurements and model results characterising this radiation environment for single event effects (SEE) in avionics. Our data, from the RaySure solid-state radiation monitor, reveal markedly different altitude profiles for low linear energy transfer (LET) and high LET energy depositions. We use models to show that the difference is caused by the influence of primary cosmic ray particles, which induce counts in RaySure via both direct and indirect ionization. Using the new Model of Atmospheric Ionizing Radiation Effects (MAIRE), we use particle fluxes and LET spectra to calculate single event upset (SEU) rates as a function of altitude from ground level to the edge of space at 100 km altitude. The results have implications for a variety of applications including high altitude space tourism flights, UAVs and missions to the Martian surface.
Hands A, Ryden KA (2017) Experimental Measurement of Low-Intensity and Long-Duration Internal Charging Behavior, IEEE Transactions on Plasma Science 45 (8) pp. 1938-1946 IEEE
We report initial results from the EU FP7 Spaces- torm project on the experimental behavior of commonly-used space dielectric materials in an electron environment where the incident electron current is significantly below safe levels specified by design standards. The realistic electron environment facility (REEF), which uses an intense strontium-90 beta-emitting radioactive source to simulate the space environment, has been recommissioned at the University of Surrey for this purpose. Using a combination of shielding and variable source-sample separation REEF can achieve a very wide dynamic range in electron current, from the very high levels associated with an extreme space weather event, down to the levels below the Euro13 pean Cooperation for Space Standardization low temperature (
Dyer C, Hands A, Ryden K, Lei F (2017) Extreme Atmospheric Radiation Environments & Single Event Effects, IEEE Transactions on Nuclear Science 65 (1) pp. 432-438 IEEE
Data from ground-level radiation monitors and cosmogenic nuclides are combined to a give a probability distribution for severe radiation events related to the well quantified event of 23 February 1956. Particle fluxes, single event effects rates and dose rates are calculated for ground-level and aerospace systems. The event of February 1956 would provide a challenge to air safety while more extreme events seen in historical records would challenge safety-critical ground systems. A new space weather hazard scale based on this event could be used to give rapid assessment of the radiation hazard using high latitude neutron monitor data.
Dyer A, Ryden K, Hands A, Dyer C, Burnett C, Gibbs M (2018) Zenith: A Radiosonde detector for Rapid-Response Ionising Atmospheric Radiation Measurements during Solar Particle Events, Space Weather 16 (3) pp. 261-272 American Geophysical Union

Solar energetic particle events create radiation risks for aircraft, notably single event effects (SEEs) 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 on-board 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 ~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 (MOCCA), taken to the CERN-EU high energy Reference Field (CERF) 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 counts s-1 cm-2 compared to 0.02 counts s-1 cm-2 at ground level.

Hands ADP, Ryden Keith, Meredith NP, Glauert SA, Horne RB (2018) Radiation Effects on Satellites During Extreme Space Weather Events, Space Weather 16 (9) pp. 1216-1226 American Geophysical Union
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
fl
uxes 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 signi
fi
cant 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 signi
fi
cant
given our increasing reliance on satellites for a vast array of services, including communication, navigation,
defense, and critical infrastructure.
Horne Richard B, Phillips Mark W, Glauert Sarah A, Meredith Nigel P, Hands Alexander, Ryden Keith, Liu Wen (2018) Realistic Worst Case for a Severe Space Weather Event Driven by a Fast Solar Wind Stream, Space Weather 16 (9) pp. 1202-1215 American Geophysical Union
Satellite charging is one of the most important risks for satellites on orbit. Satellite charging can lead to an electrostatic discharge resulting in component damage, phantom commands, and loss of service and in exceptional cases total satellite loss. Here we construct a realistic worst case for a fast solar wind stream event lasting 5 days or more and use a physical model to calculate the maximum electron flux greater than 2 MeV for geostationary orbit. We find that the flux tends toward a value of 106 cm?2·s?1·sr?1 after 5 days and remains high for another 5 days. The resulting flux is comparable to a 1 in 150?year event found from an independent statistical analysis of electron data. Approximately 2.5 mm of Al shielding would be required to reduce the internal charging current to below the National Aeronautics and Space Administration?recommended guidelines, much more than is currently used. Thus, we would expect many satellites to report electrostatic discharge anomalies during such an event with a strong likelihood of service outage and total satellite loss. We conclude that satellites at geostationary orbit are more likely to be at risk from fast solar wind stream event than a Carrington?type storm.
Jones Bryn, Dyer C, Hands Alexander, Iles R, Ryden Keith, Smith M, Stills M, Taylor G (2010) Development in Aviation Space Weather Services, AMS Poster paper
In 1998, the first Polar route test flight between Asia and North America was carried out. By the end of 2009, over 10,000 Polar flights will have taken place. However, as cross polar traffic continues to increase, the aviation industry is realising the impacts that space weather has on high-altitude, high-latitude, flights (>50ýN) and polar operations (>78ýN). Effects include disruption in High Frequency (HF) communications, satellite navigation system errors, and radiation hazards to humans and avionics.

These concerns not only apply to current operations, but become even more important at all latitudes when considered within the framework for the Next Generation Air Transportation System (NextGen), an interagency initiative to transform the U.S. air transportation system by 2025.

The AMS/SolarMetrics report, Integrating Space Weather Observations and Forecasts into Aviation Operations (published March 2007), offers recommendations to increase the safety, reliability, and efficiency of aviation operations through more effective use of space weather information. This report highlighted several policy issues that need to be addressed to ensure the best use of current and future space weather information, namely:

. Communication of space weather information

. Standardization of information and regulations

. Education and training

. Cost benefit and risk analysis

SolarMetrics is working with the airline and space transportation industries to identify and develop new integrated space weather services that will meet their demands for real-time operational decision tools and products.

This poster will present some of the operational issues raised above and how they are being tackled.

Gowen R, Smith A, Winter B, Theobald C, Rees K, Ball AJ, Hagermann A, Sheridan S, Brown P, Oddy T, Dougherty M, Church P, Gao Y, Jones A, Joy KH, Crawford I, Pike T, Kumar S, Hopf T, Wells N, Green K, Ryden Keith (2008) An update on MoonLITE, Proceedings of 59th International Astronautical Congress 7 pp. 4359-4369
MoonLITE is a proposed, UK led lunar science mission involving 4 scientific penetrators that will make in situ measurements at widely separated locations on the Moon. MoonLITE will create the first global lunar network with nodes near and far-side, and in permanently shaded crater(s). With such a network MoonLITE will be able to determine much about the interior of the Moon, including characterisation of its core. Penetrator(s) at the poles will seek and characterise frozen volatiles, possibly of cometary origin and of great importance both to human exploration and to astrobiology. MoonLITE penetrators will reach the Moon at ~300 m/s and so must be able to stand the forces associated with this impact. As part of a programme aimed to establish reliable penetrator technologies the first full-scale impact trials have been conducted and are described here.
Ryden Keith, Morris PA, Ford KA, Hands ADP, Dyer CS, Taylor B, Underwood CI, Rodgers DJ, Mandorlo G, Gatti G, Evans HDR, Daly EJ (2008) Observations of Internal Charging in Medium Earth Orbit, IEEE Trans. Plasma. Sci 36 (5) pp. 2473-2481
Ryden KA, Morris PA, Hands Alexander, Rampini R, Rodgers D (2012) Enhanced Experimental Facility to Study Internal Charging at Extremely Low Temperatures, Proceedings of 12th Spacecraft Charging Technology Conference
Lazaro D, Bourdarie S, Hands Alexander, Ryden Keith, Nieminen P (2010) Electron environment specification models for Galileo, 38th COSPAR Scientific Assembly Proceedings
Cannon Paul, Angling Matthew, Barclay Les, Curry Charles, Dyer Clive, Edwards Robert, Greene Graham, Hapgood Michael, Horne Richard, Jackson David, Mitchell Cathryn, Owen John, Richards Andrew, Rogers Christopher, Ryden Keith, Saunders Simon, Sweeting Martin, Tanner Rick, Thomson Alan, Underwood Craig (2013) Extreme space weather: impacts on engineered systems and infrastructure, In: Space Weather - full report Royal Academy of Engineering
Ryden KA, Morris PA, Hands Alexander, Alpe V (2010) Measurements of internal charging currents in MEO: 2005-2010, 11th Spacecraft Charging Technology Conference Proceedings
Pacaud Rémi, Paulmier Thierry, Sarrailh Pierre, Ryden Keith, Hands Alex, Payan Denis (2019) Study of internal charging of four commonly used polymers through experimental and numerical analysis, Journal of Applied Physics 125 (4) 045108 pp. 045108-1 AIP Publishing
This paper focuses on the study of internal charging of four space used polymers: polyetheretherketone, fluorinated ethylene propylene, polyimide films, and epoxy based material (Epoxy FR4). Experiments were carried out for each material using the GEODUR facility (Toulouse, ONERA) that mimics the geostationary space environment behind shielding. Two different irradiation currents have been applied: 1 pA/cm2 and 10 pA/cm2. 1 pA/cm2 is used to analyze the charging behavior and the intrinsic electrical properties of each polymer. 10 pA/cm2 is used to study the influence of high electric field levels on their charging behavior. In this paper, two different numerical tools used for the study of internal charging are presented: Monte-Carlo Internal Charging Tool (MCICT) and Transport of Holes and Electrons Model under Irradiation in Space (THEMIS). MCICT has been used in the space community for several years. THEMIS has been recently developed at ONERA and is compared to MCICT. Both numerical tools showed consistent results for the 1 pA/cm2 integrated current but with deviations for the 10 pA/cm2 integrated current, supposedly due to nonlinear electric field effects on charge transport. THEMIS has a more refined physical model for the conductivity than MCICT. It studies more accurately the electron-polymer interactions and the charge transport kinetics of polymers under space radiations. Subsequently, the analysis of the underlying physical phenomena responsible for the polymers? charging behaviors will be carried out with THEMIS. In addition, studying these phenomena will permit to assess the risks of electrical discharges that may occur on a spacecraft in orbit (e.g., Geostationary (GEO) spacecraft) or during an elliptic trajectory (e.g., sub-GEO) in an Electric Orbit Raising case [E. Y. Choueiri, A. J. Kelly, and R. G. Jahn, J. Spacecr. Rockets 30(6), 749?754 (1993)].
Hands Alex, Ryden Keith, Pacaud Rémi, Paulmier Thierry, Sarrailh Pierre, Payan Denis, Rodgers David (2019) Validation of Internal Charging Tools with Experiments in REEF, IEEE Transactions on Plasma Science Institute of Electrical and Electronics Engineers (IEEE)
Hands Alexander, Ryden Keith, Pacaud Remi, Paulmier Thierry, Sarrailh Pierre, Payan Denis, Rodgers David (2019) Validation of Internal Charging Tools With Experiments in REEF, IEEE Transactions on Plasma Science pp. 1-10
The objective of the European Space Agency validation of internal charging tools using the realistic electron environmental facility (REEF) project is to assess the performance of internal charging tools against experimental measurements made at the REEF facility at the University of Surrey. REEF uses an intense strontium-90 beta-emitting radioactive source to simulate the space environment. This project is complemented by parallel experiments to derive material parameters, conducted by ONERA. We report results from REEF with four different types of dielectric material and compare these results to predictions from the DICTAT, MCICT, and NUMIT internal charging simulation tools. The materials under investigation are Cirlex, PEEK, FR4, and Neoflon (FEP). We find that in many cases, the computer codes struggle to recreate REEF results, which raises significant questions over the validity of internal charging mitigation analyses. We show the advantages and disadvantages of each model and suggest what features could be added in order to improve the fidelity of their predictions.
Sandberg I., Aminalragia-Giamini S., Provatas G., Hands A., Ryden K., Heynderickx D., Tsigkanos A., Papadimitriou T., Nagatsuma T., Evans H., Rodgers D. (2019) Data Exploitation of New Galileo Environmental Monitoring Units, IEEE Transactions on Nuclear Science Institute of Electrical and Electronics Engineers (IEEE)
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 (EMU) 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 work, we present
results from the analysis of the surface charge collecting plates
and of 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
dataset, is a step forward towards the improved characterization
of MEO environment through the update of existing or the
development of new radiation environment models.
Clewer B. J., Ryden K. A., Dyer A. C. R., Hands A. D. P., Jackson D. R. (2019) A Citizen Science Network for Measurements of Atmospheric Ionising Radiation Levels, Space Weather American Geophysical Union

Historically, gathering data on atmospheric radiation levels during solar particle events (SPEs) 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 ionising dose to passengers and crew can exceed the recommended general public annual dose limits, set by the International Commission for Radiological Protection (ICRP) Barlett, Beck, Bilski, Bottollier?Depois, and Lindborg (2004), in one flight.

The Smart Atmospheric Ionising 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 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 (SPE) or GLE and the data can be used by relevant organisations to minimise potential risks.