GRBAlpha, VZLUSAT-2 and GRBBeta -- GRB observations with CubeSats
Jakub Ripa, Marianna Dafcikova, Andras Pal, Norbert Werner, Masanori Ohno, Laszlo Meszaros, Filip Munz, Balazs Csak, Gabor Galgoczi, Nikola Husarikova, Tomas Vitek, Pavel Kosik, Michaela Duriskova, Martin Kolar, Lea Szakszonova, Michal Pazderka, Filip Hroch, Martin Topinka, Yasushi Fukazawa, Hiromitsu Takahashi, Tsunefumi Mizuno, Masato Yokota, Jean-Paul Breuer, Kazuhiro Nakazawa, Hirokazu Odaka, Yuto Ichinohe, Peter Hanak, Miroslav smelko, Ivo Vertat, Tomas Urbanec, Ales Povalac, Miroslav Kasal, Jakub Kapus, Jan Hudec, Marcel Frajt, Maksim Rezenov, Vladimir Daniel, Petr Svoboda, Juraj Dudas, Martin Sabol, Robert Laszlo, Martin Koleda, Hsiang-Kuang Chang, Tsung-Che Liu, Chih-Hsun Lin, Chin-Ping Hu, Che-Chih Tsao, Kaustubha Sen, Chih-En Wu, Aaron Tohuvavohu, Suresh Sivanandam, Mark Barnet
TL;DR
The paper assesses the feasibility of CubeSat-based gamma-ray burst monitoring using CsI(Tl) detectors read out by MPPCs on three nanosatellites (GRBAlpha, VZLUSAT-2, GRBBeta) in low Earth orbit. It reports long-duration operation (multi-year lifetimes) and GRB detections across a small constellation, including the brightest GRB 221009A and GRB 230307A, with several coincident detections suggesting potential triangulation with synchronized timing. The missions provide ~360 gamma-ray transients (including GRBs, solar flares, SGRs, and one X-ray binary), and demonstrate multi-satellite GRB detections and the viability of joint localizations in future constellations. They also study the LEO radiation environment and SiPM degradation, showing that with shielding and proper design, SiPM-based detectors can function robustly over years in harsh space conditions. Overall, the results support the use of CubeSats for lightweight, long-term GRB monitoring and inform design principles for future constellations dedicated to high-energy transient astronomy.
Abstract
Results from GRBAlpha, VZLUSAT-2 and GRBBeta CubeSats and their on-board gamma-ray detectors for monitoring transients are summarised in this article. GRBAlpha was a 1U CubeSat launched in March 2021 to a 550 km altitude polar orbit carrying a CsI(Tl) scintillator gamma-ray burst (GRB) detector with a sensitive range of approximately 30-900 keV. It successfully operated for over four years until June 2025 when it de-orbited. VZLUSAT-2 was a 3U CubeSat launched in January 2022 to a 535 km altitude polar orbit and de-orbited in November 2025 after almost four years of smooth operation. It carried on board two GRB detectors very similar to the one used on GRBAlpha. Both missions have detected about 360 gamma-ray transients, including over 170 long and short gamma-ray bursts (GRBs), and including the most intense GRB ever recorded GRB 221009A and the second brightest GRB 230307A. The new family member, GRBBeta 2U CubeSat, integrated at Masaryk University, was launched in July 2024 to a 580 km altitude, 62 degree inclination orbit. It has been detecting GRBs since its launch without any trouble. Gamma-ray detectors on these nanosatellites are based on CsI(Tl) scintillator readout by silicon photomultipliers (SiPMs). These missions also provide a unique opportunity to study the radiation damage of SiPMs in the low Earth orbit environment and monitor the radiation belts. We have demonstrated that CubeSats can be used in missions lasting beyond three years and routinely detect GRBs.