Recent observations of the transient sky at all wavelengths are increasingly revealing the importance of the multi-messenger and multi-wavelength approach. The GRINTA (Gamma-Ray INternational Transient Array Observatory) mission, proposed for launch around the middle of the next decade, is conceived as a small mission with good sensitivity, excellent angular resolution and fast follow-up capability for studying transient sources at timescales from ms to hours, at the same time ensuring optimal integration with multi-messenger networks. The GRINTA mission will carry two complementary payloads to cover in total the 5 keV-10 MeV band, that will detect and localise gamma-ray bursts covering ∼ half of the sky and will be able to perform imaging surveys with sub-arcmin resolution. GRINTA will operate in synergy with the most powerful electromagnetic, gravitational wave and neutrino observatories foreseen to be operational after 2035.

The Gamma-ray Investigation of the Full Transient Sky (GIFTS) is a 6U CubeSat currently under development that is designed for the onboard detection and localization of gamma-ray bursts (GRBs), comprising six detectors and a dedicated payload board for control and data processing operations. This work is focused on the development of a GIFTS onboard payload pipeline that can reliably detect and localize the expected GRBs according to prior simulations, using data that feature representative detector rates and varieties of bursts. The generation of simulated catalogs has been established as a mechanism for developing robust processing pipelines prior to mission launch, where existing public GRB catalogs can provide a rich source of data for this activity. The Fermi-GBM GRB catalog has been used to construct a simulated GIFTS catalog containing detector readouts generated from events observed by counterpart GBM detectors, based on data products for 3405 GRBs detected by GBM between July 2008 and September 2024. Baseline payload pipeline detection and localization outputs are presented following an iterative development and evaluation process, which operates on inputs from this simulated catalog. The post-launch GIFTS mission catalog generated by the ground-based pipeline is also proposed, including the distribution of exemplar GRB products using the simulated catalog, and the development of a GIFTS Gamma-ray Data Tools package for catalog analysis.

We present a complete analysis of Fermi Large Area Telescope (LAT) data of GRB 221009A, the brightest gamma-ray burst (GRB) ever detected. The burst emission above 30 MeV detected by the LAT preceded, by 1 s, the low-energy (<10 MeV) pulse that triggered the Fermi Gamma-Ray Burst Monitor (GBM), as has been observed in other GRBs. The prompt phase of GRB 221009A lasted a few hundred seconds. It was so bright that we identify a bad time interval of 64 s caused by the extremely high flux of hard X-rays and soft gamma rays, during which the event reconstruction efficiency was poor and the dead time fraction quite high. The late-time emission decayed as a power law, but the extrapolation of the late-time emission during the first 450 s suggests that the afterglow started during the prompt emission. We also found that high-energy events observed by the LAT are incompatible with synchrotron origin, and, during the prompt emission, are more likely related to an extra component identified as synchrotron self-Compton (SSC). A remarkable 400 GeV photon, detected by the LAT 33 ks after the GBM trigger and directionally consistent with the location of GRB 221009A, is hard to explain as a product of SSC or TeV electromagnetic cascades, and the process responsible for its origin is uncertain. Because of its proximity and energetic nature, GRB 221009A is an extremely rare event.

GIFTS is a 6U CubeSat designed to detect and localise gamma-ray bursts (GRBs). Its main goal is to improve the sky coverage of existing GRB observatories and contribute to the search of electromagnetic counterparts to gravitational-wave events. GIFTS will use six CeBr _3 scintillator detectors oriented at different angles to localise GRBs based on the difference in the observed count rates. Each detector employs an array of 24 SiPMs for scintillator readout. A full-size prototype of one GIFTS detector was built and tested with gamma rays with energies ranging from 31 keV to 1.3 MeV. It showed an energy resolution of 5.4 ^∘ . The localisation error is mainly defined by statistical fluctuations in the observed count rates and becomes smaller for brighter events. Systematic localisation errors are expected to depend mainly on the accuracy of the instrument response model used by the localisation procedure. GIFTS is under development and expected to be launch ready for the next gravitational-wave observing run (O5).

Gamma-ray bursts (GRBs) are intense and short-lived cosmic explosions. Miniaturised CubeSat-compatible instruments for the study of GRBs are being developed to help bridge the gap in large missions and assist in achieving full sky coverage. CubeSats are small, compact satellites conforming to a design standard and have transformed the space industry. They are relatively low-cost and are developed on fast timescales, which has provided unparalleled access to space. This paper focuses on GMOD, the gamma-ray module, onboard the 2U CubeSat EIRSAT-1, launched on December 1st 2023. GMOD is a scintillation-based instrument with a cerium bromide crystal coupled to an array of sixteen silicon photomultipliers, designed for the detection of GRBs. The characterisation of GMOD in the spacecraft, along with the validation of an updated spacecraft MEGAlib model is presented and this approach can be followed by other CubeSats with similar science goals. The energy resolution of the flight model is 7.07% at 662 keV and the effective area peaks in the tens to hundreds of keV, making it a suitable instrument for the detection of GRBs. An investigation into the instrument’s angular response is also detailed. The results from this characterisation campaign are a benchmark for the instrument’s performance pre-launch and will be used to compare with the detector’s performance in orbit.

The LargE Area burst Polarimeter (LEAP) is a proposed Compton scattering polarimeter that will, for the first time, measure the level of polarization for a significant number of GRBs with sufficient sensitivity to determine the magnetic field structure, composition, energy dissipation mechanism of GRB jets, and determine the prompt emission mechanism of GRBs. Once approved, LEAP will be deployed as an external payload on the International Space Station (ISS) where it will measure GRB polarization over the energy range from 50–1000 keV, perform GRB spectroscopy from 20 keV to 6 MeV, and self-sufficiently determine the source direction. LEAP is uniquely suited to fill a critical gap in our knowledge regarding GRBs, by exposing the underlying physics that governs astrophysical jets and the extreme environment surrounding newborn compact objects.

BurstCube is a 6U (10 x 20 x 30 cm) CubeSat designed to detect gamma-ray bursts (GRBs) and enable multimessenger observations, scheduled to launch in early 2024. BurstCube science is informed by the coincident detection of GRB 170817A and gravitational wave (GW) 170817, which confirmed compact binary mergers as progenitors for GRBs. Future coincident detections will also provide important context to the GW measurements - namely constraining the neutron star equation of state and testing fundamental physics, while also probing the origin of GRB prompt emission. Full sky coverage in the gamma-ray regime is needed to increase the likelihood of such measurements. Once in orbit, BurstCube will expand sky coverage while rapidly providing public alerts and localization information to the community using the Tracking and Data Relay Satellite (TDRS) and General Coordinates Network (GCN). This work will describe the current status of the mission, as well as an outline of post-launch operations, performance, and science goals.

The prompt spectra of gamma-ray bursts are known to follow broadband continuum behavior over decades in energy. GRB 221009A, given the moniker the brightest of all time (BOAT), is the brightest gamma-ray burst identified in half a century of observations, and was first identified by the Fermi Gamma-ray Burst Monitor (GBM). On behalf of the Fermi-GBM Team, Lesage et al. (2023) described the initial GBM analysis. Ravasio et al. (2024) report the identification of a spectral line in part of the prompt emission of this burst, which they describe as evolving over 80 s from ∼12 MeV to 6 MeV. We report a GBM Team analysis on the Ravasio Line: 1) We cannot identify an instrumental effect that could have produced this signal, and 2) our method of calculating the statistical significance of the line shows it easily exceeds the 5σ discovery threshold. We additionally comment on the claim of the line beginning at earlier time intervals, up to 37 MeV, as reported in Zhang et al. (2024). We find that it is reasonable to utilize these measurements for characterization of the line evolution, with caution. We encourage theoretical studies exploring this newly discovered gamma-ray burst spectral feature, unless any rigorous alternative explanation unrelated to the emission from GRB 221009A is identified.

Over the last two decades, CubeSats which are nanosatellites with form factors based on units (U) of 10 x 10 x 10 cm3, have become more common in academia, enabling students to gain hands-on experience with satellite design, testing and deployment [15]. The use of Commercial-Off-TheShelf (COTS) components reduces development cost and time, making CubeSats an accessible and cost effective route to space. CubeSats are increasingly important for in-orbit demonstrations of new technologies. Further, their flexibility allows them to be configured for a wide range of science mission profiles, either as a standalone platform, as a communications relay for lunar and inter-planetary missions, such as NASA’s Mars Cube One (MarCO) satellites [14], or as a daughter spacecraft to study a near-Earth object such as LICIACube [2]. Several CubeSats for high energy astrophysics are currently in orbit and in development [9].

GRB 221009A has been referred to as the brightest of all time (BOAT). We investigate the veracity of this statement by comparing it with a half century of prompt gamma-ray burst observations. This burst is the brightest ever detected by the measures of peak flux and fluence. Unexpectedly, GRB 221009A has the highest isotropic-equivalent total energy ever identified, while the peak luminosity is at the ∼99th percentile of the known distribution. We explore how such a burst can be powered and discuss potential implications for ultralong and high-redshift gamma-ray bursts. By geometric extrapolation of the total fluence and peak flux distributions, GRB 221009A appears to be a once-in-10,000-year event. Thus, it is almost certainly not the BOAT over all of cosmic history; it may be the brightest gamma-ray burst since human civilization began.

The compact, standardised form factor of CubeSats allows for the use of commercial off-the-shelf components, reducing traditional barriers to entry, such as cost and development time. More than 1500 of these small spacecraft have been launched in the past 20 years, with improving capabilities that enable a wide range of mission profiles. The Educational Irish Research Satellite, EIRSAT-1, is a CubeSat being developed by a student-led team with goals that span education, technology demonstration and science. A comprehensive mission test plan, in which in-flight conditions are simulated, has been developed for EIRSAT-1 and implemented using an engineering qualification model of the spacecraft. In addition to verifying 41 mission requirements, the successful execution of the mission test plan established that the full satellite system can perform the intended mission. Mission testing also proved to be an invaluable tool to prepare for launch and operations, providing the team with a more complete understanding of the satellite's expected on-orbit behaviour. This work presents a detailed description of the mission test planning process and implementation, as well as key results and lessons learned. In doing so, this work aims to improve the on-orbit reliability of CubeSats by disseminating resources and good practice around mission testing.

Thermal knife HDRMs (Hold Down and Release Mechanisms) are commonly used in CubeSats and other small satellites. However, detailed information on proven designs is difficult to find. Design of a robust and reliable mechanism can present technical challenges which may only become apparent during testing, and often only when tested in a space representative environment. A custom thermal knife HDRM was designed and built for the antenna deployment module of EIRSAT-1 to deploy four coil spring antenna elements, but the same or a similar design could be repurposed quite easily to release a wide range of CubeSat deployables. In this design resistors are used to cut dyneema lines. For robustness and reliability, the thermal response of the mechanism must be well understood. To reach the melting point of the dyneema (150C) the power dissipated in the resistors must often exceed the maximum rated value. Therefore, choosing the operating current and the burn time is a careful trade-off between ensuring that the resistor reliably cuts the dyneema line and ensuring that the resistor, solder joints, PCB and nearby components are not damaged by the high temperatures. These choices are further complicated by the requirement that the mechanism operates over a range of temperatures. A thermal vacuum test campaign was carried out to better understand and characterise the thermal behaviour of the EIRSAT-1 mechanism. For the test a model of the mechanism was built with several temperature sensors installed. Two of these sensors were installed directly on the body of the resistors using a thermally conductive epoxy. Burn tests were performed in vacuum at temperatures between -37C and +56C. The test shows many interesting results including the effect of the dyneema lines on the thermal response, the possibility of desoldering the burn resistors and a comparison between the performance at ambient and vacuum conditions. Finally, a summary is given of the key technical challenges associated with this type of mechanism along with some recommendations to help make future designs more robust and reliable.

The capabilities of CubeSats have grown significantly since the first of these small satellites was launched in the early 2000s. These capabilities enable a wide range of mission profiles, with CubeSats emerging as viable platforms for certain space-based astronomical research applications. The Educational Irish Research Satellite (EIRSAT-1) is a CubeSat being developed by a student-led team as part of the European Space Agency's Fly Your Satellite! programme. In addition to its educational aims, the mission is driven by several scientific and technological goals, including a novel gamma-ray instrument for the detection of bright transient astrophysical sources such as gamma-ray bursts. This work provides a detailed description of the software development life-cycle for EIRSAT-1, addressing the design, development and testing of robust flight software, aspects of payload interfacing, and risk mitigation. A design-to-testing approach has been implemented in order to establish, prior to launch, that EIRSAT-1 can perform its intended mission. Constraints and challenges typically experienced by CubeSat teams, which can impact the likelihood of mission success, have been considered throughout and lessons learned are discussed. The aim of this work is to highlight the advanced capabilities of CubeSats while also providing a useful resource for other university-based teams implementing their own flight software.

The Educational Irish Research Satellite, EIRSAT-1, is a 2U CubeSat being implemented by a student-led team at University College Dublin, as part of the 2nd round of the European Space Agency’s Fly Your Satellite! programme. In development since 2017, the mission has several scientific, technological and outreach goals. It will fly an in-house developed antenna deployment module, along with three custom payloads, which are integrated with commercial off-the-shelf subsystems. In preparation for the flight model, a full-system engineering qualification model of the spacecraft has undergone an extensive period of test campaigns, including full functional tests, a mission test, and environmental testing at the European Space Agency’s CubeSat Support Facility in Redu, Belgium. Beyond the technical, educational, and capacity-building goals of the mission, EIRSAT-1 aims to inspire wider study of STEM subjects, while highlighting the importance of multidisciplinary teams and creating greater awareness of space in everyday life. A wide range of outreach activities are being undertaken to realise these aims. This paper provides a status update on key aspects of the EIRSAT-1 project and the next steps towards launch

Recent advancements in gamma-ray detector technology have brought new opportunities to study gamma-ray bursts and other high-energy phenomena. However, there is a lack of dissemination on the development methods, tools and techniques used in the production of instrument flight firmware. This is understandable as firmware for spacecraft payloads may be proprietary or exceptionally hardware specific and so is not always published. However, this leaves a gap in the knowledge for CubeSat teams, especially those consisting of university students who may be building a custom spacecraft payload with limited initial experience. The Gamma-Ray Module (GMOD) on-board EIRSAT-1, a 2U CubeSat in the 2nd European Space Agency Fly Your Satellite! programme, is one such instrument. GMOD features a 25x25x40mm Scionix CeBr3 scintillator, coupled to an array of 16 (4x4) JSeries OnSemiconductor MicroFJ-60035-TSV silicon photomultipliers (SiPMs) with readout provided by the SIPHRA IDE3380 application specific integrated circuit. The instrument is supported by the Gamma-Ray Module motherboard which controls and configures the instrument, providing regulated voltage and current sources as well as generating time tagged event packets and a temporary on-board flash storage. At the core of this system is the Texas Instruments MSP430FR5994 microcontroller. A custom firmware was produced for the instrument by the EIRSAT-1 team over numerous cycles of testing and development to reliably perform the long duration tasks of readout, storage and transfer of time tagged event data to the EIRSAT-1 on-board computer. Recognising the value of sharing our experiences and pitfalls on firmware development with the wider CubeSat community, this paper will provide an introduction to GMOD, with focus primarily on the development approach of the firmware. The development, testing, version control, essential tools and an overview of how the resources provided by the device manufacturer were used will be examined, such that the lessons learned may be extended to other payloads from student-led missions

BurstCube is a CubeSat Gamma-Ray Burst (GRB) detector expected to launch in 2022, significantly expanding sky coverage in the 50 keV to 1 MeV energy range and increasing the probability of detecting a gravitational wave counterpart. BurstCube will take advantage of the Tracking and Data Relay Satellite (TDRS) system in order to provide rapid public alerts and localization information, which has proven to be key to obtain valuable multi-messenger and multi-wavelength information. The BurstCube instrument is comprised of four Cesium Iodide scintillators coupled to arrays of Silicon Photomultipliers, therefore serving as a pathfinder for future missions utilizing this technology for space-based gamma-ray detection. In this presentation we will discuss the current status of the BurstCube instrument assembly, calibration and analysis pipelines. We will also describe the real-time alerts that will be sent out to the community throughout the duration of the mission.

The Gamma-Ray Module on EIRSAT-1 is a <1U CubeSat compatible instrument for the detection of high energy transient events, primarily intended for low earth orbit detection of gamma-ray bursts. The compact and low power nature of the design makes GMOD a novel instrument for GRB detection on a 2U CubeSat. The GMOD motherboard provides support to the instrument by managing a number of operation critical duties, most importantly the reliable execution of the experiment, temporary onboard flash storage and transfer of time tagged event readout to the EIRSAT-1 on-board computer. Executing these tasks is the TI MSP430FR5994 microcontroller which is loaded with a custom firmware developed for the instrument motherboard. A recent investigation into the firmware performance at fixed trigger rates proved that the firmware concept was viable for reliable detector readout. We present an investigation carried out to further quantify the performance of the firmware in a more realistic operational mode. These tests accurately simulate the rates expected by GMOD during detection of GRBs and measure performance by comparing the expected output to the actual instrument output. This is done by externally triggering the detector readout to mimic the expected rates for a range of GRB profiles and expected fluxes derived from the 4th Fermi GBM catalogue. This work evaluates the flight model firmware performance for a sample of 40 GRBs spanning a range of peak fluxes and durations.

The Educational Irish Research Satellite 1 (EIRSAT-1) is a 2U CubeSat being developed under ESA's Fly Your Satellite! programme. The project has many aspects, which are primarily educational, but also include space qualification of new detector technologies for gamma-ray astronomy and the detection of gamma-ray bursts (GRBs). The Gamma-ray Module (GMOD), the main mission payload, is a small gamma-ray spectrometer comprising a 25 mm × 25 mm × 40 mm cerium bromide scintillator coupled to an array of 16 silicon photomultipliers. The readout is provided by IDE3380 (SIPHRA), a low-power and radiation tolerant readout ASIC. GMOD will detect gamma-rays and measure their energies in a range from tens of keV to a few MeV. Monte Carlo simulations were performed using the Medium Energy Gamma-ray Astronomy Library to evaluate GMOD's capability for the detection of GRBs in low Earth orbit. The simulations used a detailed mass model of the full spacecraft derived from a very high-fidelity 3D CAD model. The sky-average effective area of GMOD on board EIRSAT-1 was found to be 10 cm2 at 120 keV. The instrument is expected to detect between 11 and 14 GRBs, at a significance greater than 10σ (and up to 32 at 5σ), during a nominal one-year mission. The shape of the scintillator in GMOD results in omni-directional sensitivity which allows for a nearly all-sky field of view.

The Fermi Gamma-ray Burst Monitor (GBM) triggers on-board in response to ∼40 short gamma-ray bursts (SGRBs) per year; however, their large localization regions have made the search for optical counterparts a challenging endeavour. We have developed and executed an extensive program with the wide field of view of the Zwicky Transient Facility (ZTF) camera, mounted on the Palomar 48 inch Oschin telescope (P48), to perform target-of-opportunity (ToO) observations on 10 Fermi-GBM SGRBs during 2018 and 2020–2021. Bridging the large sky areas with small field-of-view optical telescopes in order to track the evolution of potential candidates, we look for the elusive SGRB afterglows and kilonovae (KNe) associated with these high-energy events. No counterpart has yet been found, even though more than 10 ground-based telescopes, part of the Global Relay of Observatories Watching Transients Happen (GROWTH) network, have taken part in these efforts. The candidate selection procedure and the follow-up strategy have shown that ZTF is an efficient instrument for searching for poorly localized SGRBs, retrieving a reasonable number of candidates to follow up and showing promising capabilities as the community approaches the multi-messenger era. Based on the median limiting magnitude of ZTF, our searches would have been able to retrieve a GW170817-like event up to ∼200 Mpc and SGRB afterglows to z = 0.16 or 0.4, depending on the assumed underlying energy model. Future ToOs will expand the horizon to z = 0.2 and 0.7, respectively.