# HERMES: An ultra-wide band X and gamma-ray transient monitor on board a nano-satellite constellation

## TL;DR

HERMES is a modular nano-satellite constellation designed to detect X-ray and gamma-ray transients with high temporal resolution, aiming to advance gamma-ray burst and gravitational wave counterpart science through innovative, low-cost, rapid-deployment technology.

## Contribution

This paper presents the development of a novel nano-satellite based platform for high-energy transient detection, emphasizing modularity, rapid deployment, and technological innovation.

## Key findings

- Demonstrated the feasibility of a nano-satellite constellation for high-energy transient detection.
- Showcased the detector architecture with advanced scintillators and silicon detectors.
- Outlined the potential scientific impact on GRB and GW electromagnetic counterpart studies.

## Abstract

The High Energy Modular Ensemble of Satellites (HERMES) project is aimed to realize a modular X/gamma-ray monitor for transient events, to be placed on-board of a CubeSat bus. This expandable platform will achieve a significant impact on Gamma Ray Burst (GRB) science and on the detection of Gravitational Wave (GW) electromagnetic counterparts: the recent LIGO/VIRGO discoveries demonstrated that the high-energy transient sky is still a field of extreme interest. The very complex temporal variability of GRBs (up to the millisecond scale) combined with the spatial and temporal coincidence between GWs and their electromagnetic counterparts suggest that upcoming instruments require sub-ms time resolution combined with a transient localization accuracy lower than a degree. The current phase of the ongoing HERMES project is focused on the realization of a technological pathfinder with a small network (3 units) of nano-satellites to be launched in mid 2020. We will show the potential and prospects for short and medium-term development of the project, demonstrating the disrupting possibilities for scientific investigations provided by the innovative concept of a new "modular astronomy" with nano-satellites (e.g. low developing costs, very short realization time). Finally, we will illustrate the characteristics of the HERMES Technological Pathfinder project, demonstrating how the scientific goals discussed are actually already reachable with the first nano-satellites of this constellation. The detector architecture will be described in detail, showing that the new generation of scintillators (e.g. GAGG:Ce) coupled with very performing Silicon Drift Detectors (SDD) and low noise Front-End-Electronics (FEE) are able to extend down to few keV the sensitivity band of the detector. The technical solutions for FEE, Back-End-Electronics (BEE) and Data Handling will be also described.