The Gamma-Ray Monitor onboard the SVOM satellite

TL;DR

The Gamma-Ray Monitor onboard SVOM is a versatile instrument designed for gamma-ray burst detection, localization, and spectral analysis, successfully detecting over 100 GRBs annually since its launch in 2024.

Contribution

This paper presents the design, ground testing, in-orbit algorithms, calibration, and initial results of the GRM, establishing it as a key gamma-ray all-sky monitor.

Findings

Detected first GRB on 27 June 2024

Maintains over 100 GRBs detection per year

Validated performance through cross-instrument comparison

Abstract

The Gamma-Ray Monitor (GRM) is a key scientific payload onboard the Space-based Multi-band Variable Object Monitor (SVOM) satellite, designed specifically for the detection and study of gamma-ray bursts (GRBs). Launched into a 625 km low-Earth orbit on 22 June 2024, GRM serves as a large-area, wide-field-of-view instrument capable of observing the hard X-ray and soft gamma-ray emissions in the energy range of 15 keV to 5 MeV. Its primary scientific objectives include: promptly triggering and localizing GRBs (with particular sensitivity to short-hard GRBs), measuring spectral and temporal properties of bursts, monitoring charged particle fluxes in orbit. GRM successfully detected its first GRB (GRB 240627B) on 27 June 2024, and has since maintained a detection rate of more than 100 GRBs per year. Cross-instrument comparisons with detectors such as GECAM and Fermi/GBM have validated the performance and data quality of GRM. This paper provides a comprehensive overview of GRM instrument design, reliability verification through ground testing, in-orbit triggering and localization algorithms, performance calibration, and preliminary in-orbit results, demonstrating its capability as a versatile gamma-ray all-sky monitor.