Abstract
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.
Highlights
The atmospheric radiation environment is generated by galactic cosmic rays (GCRs) along with their interaction with the upper atmosphere
Zenith has been deployed in several environments; at 24,000 ft (7.3 km) in Met Office Civil Contingency Aircraft (MOCCA), at the accelerated radiation environment produced by CERN-EU high energy Reference Field (CERF) and on a meteorological balloon released from Camborne, UK, which ascended to an altitude of ~33 km
Zenith was deployed on a meteorological balloon from the UK Met Office’s Camborne Weather Station on 15th December 2016, where the data from Zenith was recorded by the ground station throughout the entirety of the ascent and descent until the radiosonde dropped below the ground station’s line of sight horizon at an altitude of 1 km
Summary
The atmospheric radiation environment is generated by galactic cosmic rays (GCRs) along with their interaction with the upper atmosphere. Meteorological balloon-borne space weather monitoring allows the measurement of the atmospheric radiation environment from ground level to high altitudes (~35 km) giving information of the environment’s evolution with altitude. Ambient dose equivalent can be calculated from the energy deposition spectra recorded by Zenith through processes such as “millidosimetry” outlined in Hands and Dyer (2009) Devices such as Zenith will assist the aviation industry in making informed decisions as to when action is need in response to space weather. Some airlines take action when the National Oceanic and Atmospheric Administration (NOAA) issue a S3 warning (defined as >103 protons cm-2 s-1 sr-1 (>10 MeV) measured in geostationary orbit) These events do not necessarily increase aircraft dose (Royal Academy of Engineering, 2013) where the validity of this warning system can be further determined by our instrument. Zenith has been designed to be operated, in terms of connection, data transfer and storage, in the same way as Vaisala’s own external instruments, this has been done for ease of use, allowing it to be launched by the Met Office as and when the appropriate alert is issued
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