Abstract
During a subset of solar energetic particle events, known as Ground Level Enhancement (GLE), the flux of ionising radiation can increase significantly at aviation altitudes. To date there have only been a handful of spot measurements of the enhanced GLE environment at aviation altitudes to verify scientific models. It is not currently possible to know the environment experienced and to accurately tell whether regulatory exposure limits have been exceeded during a GLE. The International Civil Aviation Authority (ICAO) have published, in their Space Weather Manual, that on-board radiation monitoring would be the most effective and accurate way of determining the exposure during a solar event. Unfortunately, without some new regulatory requirements, it is highly unlikely that airlines will install permanent detector units on their aircraft in the foreseeable future.
This thesis examines the feasibility of utilising citizen science as a novel, alternative approach, by taking advantage of modern personal devices, to monitor radiation levels at flight altitudes during Solar Particle Events (SPEs), as well as providing a way of boosting awareness about space weather and atmospheric radiation. It details the creation, and development, of a new integrated system, called the Smart Atmospheric Ionising Radiation (SAIRA) Network, where volunteers can operate newly designed detector units during their normal air travel purposes.
The work has designed, developed and tested six smartphone-connected ionising radiation detector units that can be carried on an aircraft as hand-luggage and operated through a custom-built Android application. The detectors are based upon proven silicon photodiode sensor technology and are capable of measuring an energy deposition range of 200 keV to 100 MeV. They connect to the Android smartphones via a USB connection and use a 5V Lithium-Ion (Li-Ion) USB power supply.
The SAIRA detectors were tested at the CERN-EU High Energy Reference Field (CERF) in a representative (GLE) environment and were flown on 121 flights by 30 individual volunteers. The volunteers were able to collect 436 hours worth of `background' atmospheric radiation data from 79 different routes using 22 different aircraft types and 21 airlines. The recorded flight data sets were uploaded from each smartphone after each flight via the Android application to a server. The data was made available in a publicly accessible database of flight radiation measurements on a newly built website. Additionally, the test results from the CERF facility show that the detectors are capable of reliably measuring a `Severe' GLE event, according to the ICAO scale, and the Android application is able to display a real-time warning based upon both the ICAO scale and the D-Scale.
Based on the combined results of the technical development and operational experience of the SAIRA network, it is concluded that using citizen science is a feasible, and novel, way of providing constant global radiation monitoring at aviation altitudes, but there are concerns around the financial viability and the scale of the network required. The work has created successful demonstration network and furthermore it shown how the detectors, using the inbuilt warning displays, could be used by pilots as a real-time in-flight radiation warning system. However, the cost of the detectors would need to be significantly reduced or the network have substantial financial backing for it to work as a citizen science system alone.