An important milestone has just been reached on the path towards the realisation of the LISA mission of the European Space Agency (ESA), which aims to detect gravitational waves from space. The construction of the first model of a key component of the mission, the electrode housing, has been completed under the supervision and with the €300,000 funding of the Italian National Institute for Nuclear Physics (INFN), which entrusted its construction to the company OHB Italia SpA.
LISA will be the first space-based gravitational wave detector and will follow the Earth in its orbit around the Sun. It will consist of an equilateral triangle whose vertices will host three satellites, each separated by 2.5 million kilometres, which will “exchange” laser beams, functioning as a gigantic interferometer. When a gravitational wave passes through, the distance travelled by the laser beams from one satellite to another will undergo tiny variations, detectable through the analysis of the interference between the beams.
The core of each satellite consists of two GRS (Gravitational Reference Systems), complex instruments developed with the Italian contribution to the LISA mission, through the INFN and the Italian Space Agency (ASI), and with components provided by NASA and Swiss research institutes led by ETH Zurich.
A fundamental component of the GRS is a cube made of gold and platinum, called test mass, the object on which the laser beams are reflected and whose movement will indicate the passage of a gravitational wave. Each test mass will be housed inside an electrode housing, the first model of which has just been completed.
The electrode housing is a micrometre-precision mechanical device made of molybdenum, designed to shield the test mass from external disturbances, to hold it in position using electrodes, and, with the aid of LED light, to modify its electric charge. Now that the engineering model of the electrode housing has been produced, it will be gold-plated in an operation supervised by ASI and subjected to complex ground tests.
“The engineering model will serve as a prototype for the production of the qualification models of the electrode housing, leading up to the flight models, which will need to be ready between 2030 and early 2032, in preparation for the launch of the LISA satellites planned for 2035”, explained Carlo Zanoni, engineer at the INFN-TIFPA research centre, who coordinates the development of the GRS and oversaw the technical and administrative process for the construction of this model. “Starting the supply chain for the construction of this precision masterpiece represents an essential step towards the flight programme. Equally important will be the use of this electrode housing in experimental tests that will allow us to simulate space conditions, which we will carry out both in Trento and in collaboration with CERN”.
The construction of the electrode housing prototype was funded by the INFN National Scientific Commission 2, which coordinates the Institute’s research in the field of astroparticle physics, and was overseen by researchers from the INFN-TIFPA national centre in Trento, the INFN section in Rome Tor Vergata, and the University of Trento.
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LISA is ESA’s largest scientific space mission, involving the space agencies of its member countries, including ASI, which coordinates Italy’s contribution, including that of the INFN, which is participating through the INFN-TIFPA centre and the INFN sections of Rome Tor Vergata and Florence.
