# Distributed Architectures and Constellations for \(\gamma\)-ray Burst Science
## 4 The Role of Distributed Architectures in Tomorrow's Multi-Messenger Astrophysics
### An Incomplete List of Pathfinder/Precursor Missions
#### 4.3.2 HERMES Pathfinder  
HERMES-Technologic and Scientific pathfinder (HERMES pathfinder) is an in-orbit demonstration consisting of a constellation of six 3U nano-satellites hosting simple but innovative X-ray detectors for the monitoring of cosmic high-energy transients such as GRBs and the electromagnetic counterparts of GWEs [31]. The main objective of HERMES-TP/SP is to prove that an accurate position of high-energy cosmic transients can be obtained using miniaturized hardware, with a cost at least one order of magnitude smaller than that of conventional scientific space observatories and a development time as short as a few years.  
The transient position is obtained by studying the delay time of arrival of the signal to different detectors hosted by nano-satellites on low Earth orbits [32]. To this purpose, particular attention is placed on reaching the best time resolution and time accuracy, with the goal of reaching an overall accuracy of a fraction of a micro-second [33]. The main goals of the project are: (1) join the multi-messenger revolution by providing the first mini-constellation for GRB localization with a total of six units (the first experiment of GRB triangulation with miniaturized instrumentation); (2) develop miniaturized payload technology for breakthrough science; (3) demonstrate COTS applicability to challenging missions, contribute to Space 4.0 goals, push and prepare for high-reliability large constellations.  
Figure 3 shows the HERMES pathfinder detector system during integration. The 60 GAGG scintillator crystals can be seen to the right and the \(12\ 10\times 10\) silicon drift detector mosaics used to read out the crystals to the left (see [33] and references therein for a detailed description of the HERMES pathfinder payload).  
The HERMES-TP project is funded by the Italian Ministry for Education, University and Research, and the Italian Space Agency. The HERMES-SP project is funded by the European Union's Horizon 2020 Research and Innovation Programme under Grant Agreement No. 821896.  
The consortium started the integration and testing of the first flight unit during the summer of 2021; the proto-flight model and its qualification review is foreseen for Q1 2022. The other five units will be integrated and tested during 2022 and the constellation is set to be launched to a nearly equatorial LEO in 2023.  
HERMES pathfinder is intrinsically a modular experiment that can be naturally expanded to provide a global, sensitive, all-sky monitor for high-energy transients. The next step is SpIRIT, a 6U cubesat funded by the Australian Space Agency and managed by the University of Melbourne. SpIRIT will host one HERMES pathfinder payload, and will fly  
Figure 3: HERMES pathfinder detector system during integration at Fondazione Bruno Kessler laboratories in Trento, Italy.  
on an SSO at the same time as the HERMES pathfinder, forming a constellation of seven satellites in two different orbits.