A small constellation of CubeSats for some great science

Rome, 15 March 2025 – The H.E.R.M.E.S. Constellation of the Italian Space Agency (ASI).  The High Energy Rapid Modular Ensemble of Satellites - Pathfinder Mission was successfully launched into orbit aboard the Space X Transporter 13. The launch took place this morning at 7:43 Italian time from Vandenberg Space Force Base (VSFB) in California, USA. The six CubeSats in the constellation were grouped on an ION release platform made by the Italian company D-Orbit, positioned on a Falcon 9 vector. The six nanosatellites are clustered in a Sun-synchronous orbit at an altitude of about 500-520 km, with an inclination of 97.44 degrees, and will be deployed about a week after launch with the release of one per day.

Funding for the mission came mainly from the ASI, with technical and scientific contributions from the National Institute for Astrophysics (INAF), the Politecnico di Milano (POLIMI), and the University of Cagliari (UNICA). These six CubeSats are designed to be a real breakthrough in the field of multi-messenger high-energy astrophysics and the use of nanosatellites for challenging space missions. The constellation is made up of 6 3U CubeSats, which will operate in groups of three. They will be able to detect and locate random astronomical events such as gamma ray bursts, sending a warning to the scientific community within minutes.

The President of the Italian Space Agency (ASI), Teodoro Valente, spoke for the Italian space community: "Today's launch represents another success. The sector has achieved many results on the international stage since the beginning of the year. I am particularly proud of the ASI's leading role in this challenging mission, with the care and huge support it provides for scientific developments and experiments. Thanks to the expertise of Italian academia, research and industry, H.E.R.M.E.S. has now taken an important step towards the deployment of these small but vital CubeSats. The aim is to test the concept of a "distributed sensor" in space, to demonstrate the feasibility of taking measurements in orbit by use of a modular platform: small in size and scalable, and providing a versatile, fast and economical tool."

As the President of the National Institute for Astrophysics, Roberto Ragazzoni, explained: "This small constellation introduces a new way of doing science, using small satellites that 'add up to' a telescope as large as their orbit of flight, i.e. with a diameter of almost fourteen thousand kilometres. Astronomers have already used this type of method, but this is the first time it has involved small satellites to detect X-ray transients and gamma-ray bursts, also originating from celestial bodies outside our galaxy. We're exploiting a model which can provide new ways of observing the cosmos from space."

The Rector of the Politecnico di Milano, Donatella Sciuto, also pointed out: "The Politecnico di Milano played a decisive role at various stages of the project: from the design and integration of the satellite system to the final environmental tests, using its own facilities and working with some excellent partners. The Advanced Space Technologies for Robotics & Astrodynamics (ASTRA) laboratory of the Department of Aerospace Sciences and Technologies (DAER) is a leader in aerospace research and played a decisive role. This project once again highlights the University’s ability to be right at the forefront of research and technological innovation, as well as its capacity to collaborate effectively in the face of significant challenges, helping to secure some definite results in this mission."

The six H.E.R.M.E.S. satellites The satellites in the Pathfinder Mission were designed, manufactured and integrated at the facilities of the Department of Aerospace Sciences and Technologies (DAER) of the Politecnico di Milano, while the six X-/gamma-ray monitor payloads were developed, integrated, tested and calibrated at the INAF facilities in Rome and the Fondazione Bruno Kessler in Trento. The on-board software for the payloads was developed by the University of Tübingen. The final environmental tests on the satellites were carried out by the Politecnico di Milano, using the facilities of the Politecnico itself for the mechanical testing and compliance, and those at Thales Alenia Space in Gorgonzola (MI) and INAF Rome for thermal vacuum testing.

The mission also involved some important international contributions and collaborations, as three of the six flight units were developed and created as part of the H.E.R.M.E.S.-SP project for the Horizon 2020 programme, funded by the European Commission. In addition, the ground station at Katherine in Australia is operated by the University of Tasmania under an agreement with INAF, the University of Melbourne and Masaryk University.

The constellation created under the direction of the ASI is able to continuously monitor almost the entire sky, and to transfer the coordinates of cosmic events to the scientific community in just a few minutes. This is due to its co-pointing capability, involving a constant connection with the Iridium constellation, a network of special ground stations, the Mission Operation Centre (MOC) and the Scientific Operation Centre (SOC).

The MOC of the mission, which will manage the operational phase, was created by ALTEC S.p.A. of Turin with national funding from ASI, while the SOC is hosted at the Agency's Space Science Data Centre (SSDC) in Rome. Two dedicated ground stations will be supporting the operation, one purchased and installed by the Politecnico di Milano group at the university's experimental laboratory, located in Spino D'Adda (Cremona) in Italy, and the second at Katherine.

HERMES

TECHNICAL DATA SHEET

GOAL

The concept behind the HERMES Pathfinder (High Energy Rapid Modular Ensemble of Satellites) mission is to create a constellation of nano-satellites in low orbit for monitoring the celestial sphere  to detect and locate high-energy astronomical events, such as Gamma Ray Bursts (GRBs).

An 'all-sky monitor’ sensitive to high energies such as HERMES is essential to efficiently capture such events that occur causally and emit huge amounts of energy and therefore represent potential electromagnetic counterparts of gravitational waves.

The main scientific objective of the mission is therefore two-fold. On the one hand, it is to demonstrate that cosmic transients can be routinely detected using miniaturised instrumentation installed on board CubeSat platforms; while on the other hand, it is to verify the ability to precisely locate such events using the triangulation technique.

MISSION

The flight segment of the HERMES Pathfinder mission consists of a constellation of 6 identical 3U CubeSat units, which will operate in triplets to allow the precise spatial localisation by triangulation of random high-energy events, such as Gamma Ray Bursts.

The operational orbit of the satellites is represented by a low sun-synchronous orbit (SSO) at an altitude of about 500-520 km, with an inclination of 97.44 degrees. The HERMES Pathfinder mission is expected to take 2 years, a period including the initial commissioning phase.

The operational phase of satellite observation will be more or less ongoing and, when an event occurs, each satellite will be able to send a warning to the scientific team within minutes via the IRIDIUM constellation.

SATELLITE

Each 3U satellite has a scientific payload consisting of a detector with a wide field of view and high time resolution, based on SSD (Silicon Drift Detector) technology and GAGG (Gadolinium Aluminium Gallium Garnet) scintillator crystals, sensitive to X-rays and soft-Gamma rays.

Each scientific payload was entirely designed and developed - within the framework of a specific Agreement signed with the Italian Space Agency - by the National Institute of Astrophysics (INAF) in Trieste which coordinates the activities of four other national institutes of astrophysics in Rome, Bologna, Milan and Palermo. A contribution was also made by the Institute of Astronomy and Astrophysics of the University of Tübingen, with regard to the digital electronics and on-board software; by the Fondazione Bruno Kessler in Trento, who assisted with the production of sensors and the integration of the detector system; and the University of Cagliari, who carried out the analysis and processing of high-level scientific data.

The CubeSat platform carrying the detector was instead designed and developed, under a specific Agreement signed with the Italian Space Agency, at the ASTRA laboratory of the Department of Aerospace Sciences and Technologies (DAER) of the Politecnico di Milano. It has an extremely compact and high-performance architecture.

The construction of three of the six flight units was financed by the Italian Space Agency under the respective Agreements mentioned above, while the other three were financed by the European Commission in the context of Horizon 2020, as part of the HERMES-SP project (Grant Agreement no. 821896) which involved a consortium coordinated by INAF and comprising the Politecnico di Milano, the University of Cagliari and several other European companies and research institutions.

GROUND SEGMENT

The Mission Operations Centre (MOC) is located in Turin and was set up by the Italian company ALTEC S.p.A. under a specific industrial contract, financed entirely by the Italian Space Agency.

Two ground stations with specific antenna equipment shall be used to communicate with the six flight units. The first station is located in Italy at the Experimental Laboratory of the Politecnico di Milano in Spino d'Adda (Cremona) and was built and financed under the relevant Agreement stipulated with the Italian Space Agency.

The second, instead, is located in Katherine in the Northern Territory, Australia, and was created and is managed by the University of Tasmania under an Agreement signed with the National Institute of Astrophysics, the University of Melbourne, and Masaryk University.

The scientific data acquired by the satellites and transferred to the ground are sent via the MOC to the Science Operations Centre (SOC), funded and hosted in the Space Science Data Centre (SSDC) by the Italian Space Agency in Rome.

LAUNCH

The launch of the HERMES Pathfinder mission took place on 15 March 2025 at 07:43 Italian time (6:43 UTC) from the Vandenberg Space Force Base (VSFB) in California, aboard a Falcon 9 carrier as part of SpaceX's Transporter-13 mission.

The mission made use of the ION satellite carrier of the company D-Orbit S.p.A., which provided the launch service under a specific contract financed by the Italian Space Agency.

After the launch and release of ION, deployment of the HERMES constellation will begin in about a week's time and will involve the release of one satellite per day.