HERMES-SP is a Space project based on a constellation of nano-sats in LEO. Each nano-sat will be equipped with a new miniaturized payload to detect and localize bright Cosmic high-energy transients such as Gamma-Ray Bursts (GRB) and the electromagnetic counterparts of Gravitational Wave (GW) events. Figure 1 illustrates the HERMES-SP concept.
GW170817 event marked the beginning of the multi-messenger revolution in astrophysics. The nearly simultaneous detection of GWs from merging Neutron Stars (NS) by the LIGO/Virgo and of a short GRBs by Fermi and INTEGRAL, proved that short GRBs are due to merging NSs, as hypothesized since about thirty years. Quick localization of GW-GRB event produced quick discovery of the first kilonova event by ground and space-based instrumentation. The kilonowa, being powered by the radioactive decay of r-process nuclei synthesized in the ejecta, provided breakthrough advance in our understanding of the synthesis of rare heavy elements.
The combined LIGO/Virgo – Fermi/INTEGRAL error-box was about 30deg2. The LIGO/Virgo detection indicated a very close event, ~40 Mpc, greatly limiting the volume, and therefore the number of target galaxies. An optical transient from one of these galaxies was soon discovered. For fainter events, further away, such those that will likely be provided by LIGO/Virgo in O3, O4 and O5, the volume to be searched will be ~30 times larger. This will imply >hundreds optical transients, making difficult the prompt identification of the right one for further follow-up. Fortunately, the number of X-ray transients in the same volume is much more limited (from zero to a few), making much more efficient the search for the electromagnetic counterparts of GW events in this energy band. The operation of an efficient X-ray all-sky monitor with good localization capability will thus have a pivotal role in the next decade multi-messenger astrophysics.
HERMES-SP is based on a twin project founded by the Italian Space Agency (ASI, HERMES-Technological Pathfinder). HERMES-SP is an “In Orbit Demonstrator”. Its main goal is to demonstrate that GRB detection and localization is feasible with miniaturized payloads/spacecrafts at a cost 1-2 order of magnitude lower than that of standard space projects and with a development time of a just a few years.
HERMES-SP objectives are:
OB1: develop miniaturized X-ray detectors to catch signals from X-ray transients preserving the sensitivity required for breakthrough science
OB2: provide scientifically useful data thanks to its capability to localise GRBs better or comparable with that of the Fermi GBM. Transients’ variability down to 1ms from a few keV to a few MeV will be available to scientists for further investigation
OB3: demonstrate the COTS applicability to challenging space missions: HERMES-SP will assess and apply a production life cycle aimed at increasing the COTS reliability still limiting the time to space and cost.
OB4: contribute to the Space 4.0 goals: HERMES-SP will contribute to identify and standardize new and innovative approaches to manufacture, assemble and test miniaturized components.
OB5: enlarge and strengthen the space distributed architectures and mega-constellations applicability and reliability: to gain the required precision in GRB localization requires a sensors distribution covering the full sky
OB6: prepare for a proposal to the European Space Agency (as well as to National Agencies) for the realization of a real observatory based on distributed instrumentation during the 2020’, the HERMES Full Constellation
