The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a Chinese-French satellite dedicated to the observation and study of Gamma-Ray Bursts (GRBs) and other variable sources. Among the four scientific payloads onboard SVOM, the Gamma-Ray Monitor (GRM) is designed to detect GRBs in the 15 keV to 5 MeV energy range. The final performance of GRM can be affected by the space environment background during the flight. In this paper, the authors present the in-orbit background simulation results by using the GEANT4 Monte-Carlo simulation toolkit. Additionally, we studied the Earth occultation effect of the space background due to the anti-solar pointing strategy of SVOM. The total background count rate of each spectrometer of GRM fluctuates between about 840 counts/s and 1341 counts/s, and is dominated by the cosmic X-ray background. Finally, we discuss the emission lines of the background and their potential use for in-orbit calibration of GRM. Our simulation study results can help to understand the impact of the space radiation environment on GRM with the latest geometrical model and can be further compared and updated with the real in-orbit measurement in the future.

中文翻译：

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SVOM/GRM在轨背景模拟研究

天基多波段天文变天体监测仪（SVOM）是一颗中法卫星，致力于伽马射线暴（GRB）等变源的观测和研究。在 SVOM 上的四个科学有效载荷中，伽马射线监视器 (GRM) 旨在检测 15 keV 至 5 MeV 能量范围内的 GRB。GRM的最终性能会受到飞行过程中空间环境背景的影响。在本文中，作者使用GEANT4 Monte-Carlo仿真工具包展示了在轨背景仿真结果。此外，我们研究了由于SVOM的反太阳指向策略导致的空间背景对地球的掩星效应。GRM每台光谱仪的总本底计数率在840次/秒到1341次/秒左右波动，以宇宙X射线本底为主。最后，我们讨论了背景的发射线及其在 GRM 在轨校准中的潜在用途。我们的模拟研究结果有助于通过最新的几何模型了解空间辐射环境对GRM的影响，并可以在未来与实际在轨测量进一步对比和更新。