We report on the on-orbit performance of the Glowbug instrument, which operated on the International Space Station (ISS) from March 2023 to April 2024. Glowbug is a NASA Astrophysics Research and Analysis (APRA) funded instrument built by the U.S. Naval Research Laboratory (NRL) in Washington, DC, and is the pathfinder instrument for the upcoming NASA StarBurst Multimessenger Pioneers mission. Glowbug was launched to the ISS on the 27th Commercial Resupply Services mission operated by SpaceX (SpX-27) as part of the Department of Defense Space Test Program (STP) H9 pallet. Glowbug’s primary science objective is the detection and localization of short Gamma-Ray Bursts (GRBs), which are the result of mergers of stellar binaries involving a neutron star with either another neutron star or a black hole. Detection is enabled by 12 large area (150mm x 150mm), inorganic scintillator panels (thallium-doped cesium iodide, CsI:Tl), arrayed on the surface of a half cube. Each panel is read out on one edge by a 1x21 array of onsemi J-series 6mm x 6mm silicon photomultipliers (SiPMs). Additionally, within the half cube, resides two inorganic scintillators, Cs2LiLaBr6:Ce (CLLB), and a small plastic (EJ-200) scintillator on the exterior used as an South Atlantic Anomaly (SAA) entry and exit detector, both of which are read out by an array of SiPMs on one face of each detector unit. We discuss the Glowbug on-orbit results for one year’s worth of data, in terms of on-orbit operations, SiPM performance in low-earth orbit (LEO), and GRB detections.
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