Quantifying particle background and GRB induced signal in Low Earth Orbit for the CAMELOT CubSsat mission with Geant4 simulations

Gabor Galgoczi ^1,2 Masanori Ohno ^1,3 Norbert Werner ^1,3,11 Jakub Ripa ^1,9 Andras Pal ¹⁰ Laszlo Kiss ¹⁰ Yasushi Fukazawa ³ Tsunefumi Mizuno ³ Hiromitsu Takahashi ³ Koji Tanaka ³ Nagomi Uchida ³ Kento Torigoe ³ Zsolt Frei ¹ Norbert Tarcai ⁴ Kazuhiro Nakazawa ⁵ Teruaki Enoto ⁶ Hirokazu Odaka ⁷ Yuto Ichinohe ⁸

¹Department of Atomic Physics, Eötvös University, Hungary
²Department of High Energy Physics, Wigner RCP, Hungary
³School of Science, Hiroshima University, Japan
⁴Company, C3S LLC, Hungary
⁵Space Astronomy Laboratory, Nagoya U., Japan
⁶Department of Astronomy, Kyoto University, Japan
⁷Department of Physics, The University of Tokyo, Japan
⁸Department of Astronomy, Rikkyo University, Japan
⁹Astronomical Institute, Charles University, Czech Republic
¹⁰Hungarian Academy of Sciences, Konkoly Observatory, Hungary
¹¹Department of Theoretical Physics and Astrophysics, Masaryk University, Czech Republic

The first detection of gravitational waves (GW) in 2015 marked a new
era in multi-messenger astronomy. The investigation of gravitational
wave events in the electromagnetic (EM) regime is still a challenge.
Cubesats Applied for MEasuring and LOcalising Transients (CAMELOT) is
a fleet of nanosatellites that is currently under development. CAMELOT
is expected to perform all-sky monitoring and timing based
localisation of short gamma-ray bursts (GRBs) associated with neutron star
mergers that are among the most important sources of GWs. The precise
localisation of these exciting events will enable quick follow up
observations at other wavelengths, providing valuable multi-messenger
information.

Satellites are exposed to a wide range of radiation including
electrons, photons, protons, heavy nuclei and neutrons. In low-Earth
orbit the flux of trapped charged particles might vary by six orders
of magnitude. In the case of small CubeSats the utilization of thick
shielding or anticoincidence shield is not an option. Therefore, the
quantification and minimisation of particle background is vital for
scientific missions that aim to detect events with a low
signal-to-noise ratio. In order to quantify the background and the
expected signal of GRBs a series of detailed Geant4 simulations were
carried out. The mass model of the CAMELOT CubeSat was imported into
Geant4 and the energy spectra for the different components of
radiation in low-Earth orbit for a number of different orbits were
determined using SPENVIS and other models.