Dottorato - PhD thesis
Area tematica: RSN3, RSN4, RSN5
Referente: Fabrizio Fiore
Titolo: A versatile instrument for X and gamma observations of the Universe and planetary surfaces
Decorrenza: 14 aprile 2025
The INAF HERMES team designed, developed, integrated and tested an advanced X-Ray and gamma-ray spectrometer which reached space on board of the SpIRIT satellite in December 2023. SpIRIT is a 6U cubesat funded by the Australian Space Agency and managed by University of Melbourne. Since then it is working with good performances, validating the design and the integration procedures.
The same instrument is on board the HERMES Pathfinder mission, launched on March 15th 2025 (www.hermes-sp.eu). HERMES Pathfinder consists in six 3U cubesats with the main goal of showing that bright high energy transients such as Gamma Ray Bursts can be routinely detected by miniaturized instrumentation on board cubesats, and that their position in the sky can be determined through the triangulation technique. The project is funded by the Italian Space Agency (ASI) and by the European Commission through a Horizon2020 grant.
The payload is based on the so called Siswitch design, where Silicon Drift Detectors read out X-rays directly from the sky and optical photons produced by gamma-rays in GAGG:CE scintillator crystals. This ensures a unique wide band from a few keV to a few MeV, covered by a single instrument. The other peculiarity of the payload is its exquisite temporal resolution, <1microsec. Each payload includes a mosaic of 120 SDD and 60 scintillator crystals, divided in four quadrants. This ensures redundancy and the possibility to use anti-coincidence techniques to reduce the particle background. The total collecting area is of about 50cm2.
The same payload has been proposed also for planetary surface studies. In particular two projects are today active and funded: the ASI TASTE (Terrain Analyzer and Sample Tester Explorer) and the INAF PRORIS PROGReX (PROspecting the Moon with Gamma-Rays & X-rays) projects.
The TASTE mission will study Deimos, one of the moons of Mars, with the goal of assessing its origin, distinguishing between two main scenarions: a captured asteroid or a debris of Mars due to the impact of a third body with the Mars surface. The X-ray and gamma-ray instrument will obtain broad band spectroscopy of the Deimos surface, from a few keV to about 3 MeV, with the goal of measuring abundances of key elements such as Calcium, Titanium, Iron, Thorium, Potassium, Uranium. Abundance ratios can help in distinguishing between the two possibilities for the Deimos origin.
The TASTE project is currently in a phase B study ending in September 2026. If accepted for further developments TASTE may be launched by the end of this decade.
The PRORIS PROGReX started on March 2025 and it is funded for three years. The main goal is to develop a payload to be used on the surface of the Moon on board a rover for resource prospecting. PROGReX exploits the very broad band of the X-ray and gamma-ray spectrometer to monitor the Thorium line and assess the area where the Thorium abundance is higher. It is well know that critical elements like Rare Earths (REE) are usually present in Thorium reach terrains. The X-ray spectrometer, assisted by an X-ray source, will then be used to perform X-ray Fluorescence Spectroscopy (XRF) of samples to assess the presence of REE or other precious metals such as Titanium and Platinum Group Elements (PGE).
The PhD student will be involved in the INAF-OATs team active on the three projects. The activities that will be followed by the PhD student will be:
1) study of the in flight performances of the X-ray and gamma-ray spectrometer on board SpIRIT and HERMES Pathfinder. In particular, the study of the degradation of the SSD sensors used due to radiation damage and the performance of the ASIC read out electronics. The PhD student will also be included in the group of “Burst Advocates” with the task of following each GRB detected by the constellation.
2) Laboratory test and calibration of the breadboard including SDD and ASIC that will be developed for the TASTE Phase-B study.
3) Laboratory tests and calibrations of the breadboards and demonstration model that will be developed for the PRORIS PROGReX project. In particular, XRF tests on suitable samples. The activity will include set-up of the experiments and the development of analytic and numeric models to be compared to the laboratory results.
We expect the PhD student to gain considerable insight in both high energy astrophysics data analysis, laboratory work on X-ray and gamma-ray detectors, analytic and numerical modelling. The work will be carried out in close collaboration with the INAF-OATs team, but also in collaboration with the INAF teams of Bologna, Roma, Firenze e Napoli, and Fondazione Bruno Kessler.
