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RAVI-2017: A solar proton fluence monitor for LEO nanosatellite missions based on COTS electronics.
In: (69th International Astronautical Congress: #InvolvingEveryone, 1-5 October 2018, Bremen). 2018. ( ; 2018-October)
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Protons of a wide energy distribution between 100 keV - 250 MeV originated from Coronal Mass Ejection (CME) from sun are trapped within the inner shell of the Van Allen belt surrounding our earth. Consequently, all spacecrafts, in particular nanosatellites operating in low earth orbit (LEO) environment are exposed to those trapped protons of solar origin. Highest radiation exposure takes place when the spacecrafts pass through the South Atlantic Anomaly (SAA) region. High-energy protons trigger irreparable displacement damage (IDD) in unbiased Gallium Arsenide (GaAs) Light-Emitting Diode (LED). The physical process is known as NIEL (non-ionising-energy-loss). The IDD results in reduction of light emission of the LED. Based on this phenomenon the authors had developed a lightweight, ultra-low-power consuming proton fluence monitor for space applications. Commercial off the shelf (COTS) components: combination of a GaAs-LED optically coupled to a Light-to-Frequency converter (LFC) chip was the core of Ravi-2017 proton fluence monitor. The device was calibrated by irradiating the LED with 180 MeV proton beam form a medical cyclotron at various dose levels. The resulting LED light output was detected with the LFC as a function of proton dose (fluence). The results were parameterised for the realistic NASA radiation belt models AP8-Max and AP8-Min and proton NIEL distribution function in GaAs-LED. The highest detectable integrated proton fluence (protons.cm -2 ) was evaluated to be 1.17 10 9 and 1.01 10 9 for AP8-Max and AP8-Min models respectively. The footprint, mass and average power consumption of proton fluence monitor were 0.16 cm 2 , 0.28 g and ~6.8 mW respectively. This makes the GaAs-LED based solar proton fluence monitor RAVI-2017 ideally suited for proton event monitoring during geomagnetic storm (space weather forecasting) on board LEO nanosatellites of short lifetime, usually 6 -18 months.
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Publication type Article: Conference contribution
Keywords Cots Electronics ; Displacement Damage ; Gaas-led ; Nanosatellite ; Proton Fluence Monitor ; Space Weather Forecast
ISSN (print) / ISBN 0074-1795
Conference Title 69th International Astronautical Congress: #InvolvingEveryone
Conference Date 1-5 October 2018
Conference Location Bremen
Quellenangaben Volume: 2018-October
Institute(s) Institute of Radiation Medicine (IRM)