EIRFLAT-1: A FlatSat platform for the development and testing of the 2U CubeSat EIRSAT-1

The Educational Irish Research Satellite (EIRSAT-1) is a 2U CubeSat being designed, built and tested at University College Dublin. A FlatSat platform known as EIRFLAT-1 has been constructed to enable the testing and development of the CubeSat. EIRFLAT-1 facilitates the electrical connections between CubeSat components while leaving key interfaces accessible for test equipment and allowing for the hot swapping of components. Commercial Off The Shelf and in-house developed hardware has been tested using EIRFLAT-1 at component, subsystem and full system level. In addition, the FlatSat has been used for flight software development. This paper describes the design of EIRFLAT-1 including electrical and mechanical components and additional ground support equipment developed to assist in the testing and development activities. EIRFLAT-1 has proven to be an invaluable tool for testing and has led to the discovery of issues and unexpected behaviour with flight hardware which would have contributed to schedule delays if undiscovered until after the satellite was assembled. Moreover, EIRFLAT-1 facilitated early and incremental testing of both software and operations procedures. The schematics for the electrical design of EIRFLAT-1, which is compatible with all CubeSat Kit PC/104 components, has been made publicly available for use by other educational CubeSat team

Experiences in firmware development for a CubeSat instrument payload

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 mission

Thermal characterization testing of a robust and reliable thermal knife HDRM (Hold Down and Release Mechanism) for CubeSat deployables

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

Update on the status of the Educational Irish Research Satellite (EIRSAT-1)

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 launc

Two Dimensional Clustering of Swift/BAT and Fermi/GBM Gamma-ray Bursts

Studies of Gamma-ray Burst (GRB) properties, such as duration and spectral hardness, have found evidence for additional classes beyond the short-hard (merger) and long-soft (collapsar) prototypes. Several clustering analyses of the duration-hardness plane identified a third, intermediate duration, class. In this work, Gaussian Mixture Model-based (GMM) clustering is applied to the Swift/BAT and Fermi/GBM samples of GRBs. The results obtained by the hierarchical combination of Gaussian components (or clusters) based on an entropy criterion are presented. This method counteracts possible overfitting arising from the application of Gaussian models to non-Gaussian underlying data. While the initial GMM clustering of the hardness-duration plane identifies three components (short/intermediate/long) for the Swift/BAT and Fermi/GBM samples, only two components (short/long) remain once the entropy criterion is applied. The analysis presented here suggests that the intermediate duration class may be the result of overfitting, rather than evidence of a distinct underlying population

Two Classes of Gamma-ray Bursts Distinguished within the First Second of Their Prompt Emission

Studies of Gamma-Ray Burst (GRB) properties, such as duration and spectral hardness, have found evidence for additional classes, beyond the short/hard and long/soft prototypes, using model-dependent methods. In this paper, a model-independent approach was used to analyse the gamma-ray light curves of large samples of GRBs detected by BATSE, Swift/BAT and Fermi/GBM. All the features were extracted from the GRB time profiles in four energy bands using the Stationary Wavelet Transform and Principal Component Analysis. t-distributed Stochastic Neighbourhood Embedding (t-SNE) visualisation of the features revealed two distinct groups of Swift/BAT bursts using the T100 interval with 64 ms resolution data. When the same analysis was applied to 4 ms resolution data, two groups were seen to emerge within the first second (T1) post-trigger. These two groups primarily consisted of short/hard (Group 1) and long/soft (Group 2) bursts, and were 95% consistent with the groups identified using the T100 64 ms resolution data. Kilonova candidates, arising from compact object mergers, were found to belong to Group 1, while those events with associated supernovae fell into Group 2. Differences in cumulative counts between the two groups in the first second, and in the minimum variability timescale, identifiable only with the 4 ms resolution data, may account for this result. Short GRBs have particular significance for multi-messenger science as a distinctive EM signature of a binary merger, which may be discovered by its gravitational wave emissions. Incorporating the T1 interval into classification algorithms may support the rapid classification of GRBs, allowing for an improved prioritisation of targets for follow-up observations

Mission Test Campaign for the EIRSAT-1 Engineering Qualification Model

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

Mission Test Campaign for the EIRSAT-1 Engineering Qualification Model

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 Vacuum Test Campaign of the EIRSAT-1 Engineering Qualification Model

CubeSats facilitate rapid development and deployment of missions for educational, technology demonstration, and scientific purposes. However, they are subject to a high failure rate, with a leading cause being the lack of system-level verification. The Educational Irish Research Satellite (EIRSAT-1) is a CubeSat mission under development in the European Space Agency’s (ESA) Fly Your Satellite! Programme. EIRSAT-1 is a 2U CubeSat with three novel payloads and a bespoke antenna deployment module, which all contribute to the complexity of the project. To increase the likelihood of mission success, a prototype model philosophy is being employed, where both an engineering qualification model (EQM) and a flight model of EIRSAT-1 are being built. Following the assembly of the EQM, the spacecraft underwent a successful full functional test and month-long mission test. An environmental test campaign in ESA Education Office’s CubeSat Support Facility was then conducted with the EQM where both vibration and thermal verification test campaigns were performed. The focus of this paper is the thermal testing and verification of the EIRSAT-1 EQM. Over three weeks, the EQM was subjected to one non-operational cycle, three and a half operational cycles, and a thermal balance test in a thermal vacuum chamber. After dwelling at each temperature extreme, functional tests were performed to investigate the performance of the spacecraft in this space representative environment. The approach to planning and executing the thermal testing is described in detail including the documentation required, set up of the test equipment, and determination of the test levels. Overall, the campaign demonstrated that the mission can successfully operate in a space environment similar to that expected in orbit, despite encountering a number of issues. These issues included a payload displaying anomalous behaviour at cold temperatures and needing to redefine test levels due to an insufficient understanding of the internal dissipation in the spacecraft. A total of two major and three minor non-conformances were raised. Crucially, these issues could not have been found without thermal testing, despite the comprehensive ambient tests performed. The main results and lessons learned during this thermal test campaign are presented with the aim of guiding future missions on optimal approaches in organising and executing the thermal testing of their CubeSats