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High Energy Rapid Modular Ensemble of Satellites, Scientific Pathfinder

Periodic Reporting for period 1 - HERMES-SP (High Energy Rapid Modular Ensemble of Satellites, Scientific Pathfinder)

Reporting period: 2018-11-01 to 2020-04-30

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 in 2017 marked the beginning of the multi-messenger revolution in astrophysics. New observations of GW added up to traditional electromagnetic observations from the same astrophysical source. The nearly simultaneous detection of GWs from merging Neutron Stars (NS) by the LIGO/Virgo and of a short GRBs by the Fermi and INTEGRAL sats, 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 optical and near infrared 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 of the order of 30 square degrees. Luckily, the LIGO/Virgo detection indicated a very close event, ~40 Mpc, greatly limiting the volume, and therefore the number of target galaxies (about 50 galaxies were present in the volume and were subject of optical follow- ups). An optical transient from one of these nearby galaxies was soon discovered. Two were thus the key elements that allowed the discovery and localization of the optical transient associated to the GW event: a) the prompt X-ray detection, and b) the very limited volume that had to be searched. 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 hundred/thousands 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 then 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 (ESA class M mission, NASA Explorer mission) and with a development time of a just a few years, compared with 10-15 years of standard space projects.

HERMES-SP objectives are:

OB1: refine and develop miniaturized X-ray detectors to catch signals from GRBs and other X-ray transients related to GWEs monitoring with the challenge to fit in a nano-sats, 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. GRBs and other transients’ variability down to 1s and in a very broad energy band, from a few keV to a few hundred keV will be available to scientists for further investigation

OB3: demonstrate the COTS applicability to challenging space missions: CubeSats represent a cluster of disruptive technologies, risky at the time being because of COTS inadequacy to space environment
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
The first year was dedicated to:

- finalize the mission design, the mission requirements, the payload requirements and the system requirements
- finalize the mission analysis of the full constellation (HERMES-TP+HERMES-SP, six satellites)
- validate of the design of the payload and service module developed under ASI lead
- development and tests of breadboards of subsystems

Activities produced final designs of payload and service module.
Massive simulations were carried out and analyzed to assess both payload and service module performances.

Next 6 months were dedicated to the development of the payload Demonstration Model (DM) and SM Engineering Model (EM).

Payload DM is aimed at:
• test production processes of elements and subsystems;
• test integration procedures;
• perform complete functional tests on a representative system;
• perform environmental tests at qualification level for characterization.

The SM EM is aimed at testing custom software on OBDH and ADCS SM subsystems.
As of today, the missions dedicated to X-ray and Gamma-ray transients are NASA SWIFT and Fermi, ESA INTEGRAL, and ASI Agile observatories. All these observatories are working nominally after more than 15, 17, 12 and 13 years after launch. Their predicted lifetime would extend the missions through the 2020’, but equipment is aging and it is not known how long they will keep full functionalities. Missions aimed at localizing high energy transients were and will be proposed to NASA (Midex class) and ESA (M class). HERMES offers a fast track and less expensive complement for bright events to such more complex and ambitious mission.

HERMES-SP will develop payloads, SM and subsystems that, while maintaining flexibility and re-configurability, are high-performing, so to achieve its ambitious scientific goals: demonstrate in space that accurate localization of GRBs are feasible with miniaturized instrumentation hosted by nano-sats. This experiment will quantitatively show that a full constellation (~tens/hundred units) has the capability to provide breakthrough observations (arcmin transient localization, investigation of the temporal structure of transients in the today basically unexplored window between ~1μsec and 1msec. Project main impact will therefore be the verification that breakthrough space science can be achieved using an innovative disruptive approach, producing a radical change in the European system.

According to results of the EU FP7-SPACE-2012 NANOSAT project there are significant obstacles that are hindering nano-satellites development in Europe:
• Lack of awareness about nano-satellites capabilities
• Lack of coordination
• Incomplete understanding of potential markets
• Fragmented overview of best practices
HERMES-SP will show that these shortcomings/problems can be overcome, thereby complying with the EU guidelines.