## 8 Conclusions  
The characterisation of the flight model instrument provides a comprehensive understanding of the instrument's behaviour pre-launch. Initially, an energy calibration was performed on GMOD to map the ADC channel values to energy. Then, the properties of the detector were determined, with the FM having an energy resolution of 7.07% at 662 keV. The effective area as a function of energy and incident angle was investigated, which is important for interpreting the downlinked science data during the mission. The effective area of GMOD peaks in the energy range of tens to a few hundred keV, as is required by the specifications of our scientific case for GRB detection. As expected, the detector is most sensitive on the faces with minimal obstruction and the least sensitive faces are those where gamma-ray photons must first pass through the CubeSat stack or the PCBs in the detector assembly. In addition to these measurements with the physical flight model, the EIRSAT-1 MEGAlib model was updated to reflect the new configuration of GMOD in the flight model. This updated model was validated by simulating the measurements made in the lab and confirming consistency between the simulated and physical results. This approach to characterising an instrument for GRB science can be followed by other CubeSats with similar science goals. The results from this characterisation campaign can be used for comparison with the detector's performance in orbit. In reference [29], simulations performed with the original MEGAlib model predicted that GMOD will detect 11-14 GRBs at a significance greater than 10\(\sigma\) during a nominal one-year mission. Future work would include performing these simulations with the updated MEGAlib model presented in this paper and producing the response files for spectral fitting.  
Conceptualization, D.M. ([PERSON]), A.U., J.M., M.D., B.S. and S.M.; Methodology, R.D. and J.T.; Software, M.D.; Validation, A.U.; Formal analysis, R.D.; Investigation, R.D. and D.M. ([PERSON]); Resources, J.M. and J.T.; Writing--original draft, R.D.; Writing--review & editing, R.D., A.U., J.M., M.D., J.T., C.d.B., L.H., D.M. ([PERSON]), B.S. and S.M.; Supervision, D.M. ([PERSON]), A.U., L.H. and S.M.; Project administration, L.H., D.M. ([PERSON]) and S.M.; Funding acquisition, L.H., D.M. ([PERSON]) and S.M. All authors have read and agreed to the published version of the manuscript.  
The EIRSAT-1 project is carried out with the support of ESA's Education Office under the Fly Your Satellite! 2 programme. The authors acknowledge the guidance from [PERSON] of the ESA PRODEX Office. The authors acknowledge all students who have contributed to EIRSAT-1 and support from Parameter Space Ltd. R.D., M.D., D.M. and J.T. acknowledge support from the Irish Research Council (IRC) under grants GOIPG/2019/2033, GOIP/2018/2564, GOIPG/2014/453 and GOIPG/2014/684, respectively. [PERSON], [PERSON], [PERSON] and [PERSON] acknowledge support from Science Foundation Ireland under grant 17/CDA/4723. [PERSON] and [PERSON] acknowledge support of Science Foundation Ireland grant 21/FFP/A/9043. [PERSON] acknowledges support from SFI under grant 19/FFP/6777 and support from the EU H2020 AHEAD2020 project (grant agreement 871158). This study was supported by the European Space Agency's Science Programme under contract 4000104771/11/NL/CBi and by the European Space Agency's PRODEX Programme under contract number C 4000124425.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author. The datasets presented in this article are not readily available because the data are part of an ongoing study. Requests to access the datasets should be directed to the corresponding author.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.