# Background for a gamma-ray satellite on a low-Earth orbit

## TL;DR

This paper models the various background components affecting a gamma-ray satellite in low-Earth orbit, considering primary and secondary particles, and evaluates activation effects using simulations relevant for future missions.

## Contribution

It provides a comprehensive background model for low-Earth orbit gamma-ray satellites, including corrections for geomagnetic effects and activation simulations for a proposed mission.

## Key findings

- Primary protons dominate activation contributions.
- Long-term activation from the South Atlantic Anomaly is significant at high inclinations.
- The background model is available as an open-source Python class.

## Abstract

The different background components in a low-Earth orbit have been modeled in the 10 keV to 100 GeV energy range. The model is based on data from previous instruments and it considers both primary and secondary particles, charged particles, neutrons and photons. The necessary corrections to consider the geomagnetic cutoff are applied to calculate the flux at different inclinations and altitudes for a mean solar activity. Activation simulations from such a background have been carried out using the model of a possible future gamma-ray mission (e-ASTROGAM). The event rates and spectra from these simulations were then compared to those from the isotopes created by the particles present in the South Atlantic Anomaly (SAA). The primary protons are found to be the main contributor of the activation, while the contributions of the neutrons, and that of the secondary protons can be considered negligible. The long-term activation from the passage through the SAA becomes the main source of background at high inclination (i$\gtrsim10^\circ$). The used models have been collected in a Python class openly available on github.