## 1 Introduction  
Gamma-ray bursts (GRBs) are violent, bright and brief explosions in the universe resulting from the death of a massive star or the collision of two compact objects, such as neutron star-neutron star or neutron star-black hole mergers [1, 2]. The breakthrough coincident detection of electromagnetic signals (from radio to gamma rays) and gravitational waves in 2017 facilitated a new way to probe these complex events [3, 4]. A major challenge to the future of gamma-ray astronomy and the progression of GRB science is the lack of new missions. The legacy and current gamma-ray missions have excelled in advancing the understanding of these objects but the majority are operating beyond their nominal lifetimes [5, 6, 7, 8]. Additionally, current gamma-ray observatories cannot provide full-sky coverage in a single observation for these brief isotropic explosions, which is critical for future coincident detections. Obtaining a population of GRB/gravitational wave joint detections will be important in determining the characteristics of the different types of GRBs, confirming other theorised progenitors and the extracted properties can be used to search archival data (e.g., [9]) for similar candidates. Furthermore, increasing the number of joint detections could constrain the neutron star equation of state, advance the understanding of the origin of the heaviest elements in the universe and provide new insights into fundamental physics such as investigating the difference between the speed of gravity and the speed of light [3; 10]. CubeSats are small-scale satellites, usually conforming to a design standardisation, defined by Cal Poly specifications [11]. CubeSats have grown in popularity in recent years due to their science and technology demonstration capabilities [12; 13; 14; 15]. CubeSats were originally developed as an educational tool [16; 17], resulting in the production of commercial-off-the-shelf (COTS) components. COTS components can be used for the fundamental subsystems of the satellite, e.g., power, communications and onboard computer (OBC), allowing for more resources to be applied to the science objectives of the mission [18]. CubeSats are relatively low-cost and have short launch timescales [19], making them ideal candidates to bridge the gap in gamma-ray missions during the multi-messenger era [20]. In addition to the current large-scale gamma-ray missions, a fleet of GRB-detecting CubeSats could allow for the adequate detection and localization of GRBs, and increased sky coverage. SmallSats with GRB detection and localisation capabilities are in development, e.g., BurstCube [21; 22], MoonBEAM [23], HERMES [24], GRBAlpha [25] and CAMELOT [26]. The Educational Irish Research Satellite (EIRSAT-1) is a 2U CubeSat with a primary payload, the gamma-ray module, GMOD, developed for the detection of GRBs [27; 28] at energies 60 keV to \(\approx\)2 MeV, as presented in Figure 1. GMOD is a \(<\)1 U scintillation-based detector and consists of two main components: the detector assembly and the GMOD Motherboard (MB) [29; 30; 31]. The detector assembly holds the CeBr\({}_{3}\) scintillation crystal (25 mm \(\times\) 25 mm \(\times\) 40 mm), which interacts with gamma-ray photons from GRBs to produce optical photons, which are collected by a tiled array of 16 silicon photomultipliers (SiPMs). The outputs from the SiPMs are read out and digitised by an application-specific integrated circuit (ASIC), produced by Integrated Detector Electronics AS (IDEAS), Oslo, Norway called SIPHRA (Silicon Photomultiplier Readout ASIC) [32]. The GMOD motherboard was developed in-house [33; 34] and supports the electronics for power and the readout of the detector assembly. The GMOD MB converts the channel data into time-tagged events (TTEs). TTEs are generated for the 16 individual channels of SIPHRA and for the sum channel (sum of 16 channels). Both sum and 16 channel TTEs are sent in pages to OBC.