Speaker
Description
The ASTRI Mini-Array is an International collaboration, led by INAF, that is constructing and operating an array of nine Cherenkov Telescopes at the Teide Observatory (Tenerife, Spain). The ASTRI Stellar Intensity Interferometry Instrument (SI3) is a fast single-photon-counting instrument for performing intensity interferometric observations of bright stars with the ASTRI Mini-Array. It will exploit the simultaneous 100-700 m baselines of the array to achieve angular resolutions below 100 microarcsec in the visible band and a dense coverage of the U-V plane. SI3 is the first implementation of very narrow-band, multi-channel intensity interferometry in photon counting on Cherenkov telescopes with sub-nanosecond sampling, paving the way to second-generation instruments for the Cherenkov Telescope Array Observatory. The basic concept of SI3 is to inject light into a multimode optical fiber bundle at the telescope focal plane, work on the output beam to efficiently insert very narrow-band (~1 nm) filters, and finally focus light into modern single-photon Silicon detectors, fully exploiting their ∼100-ps resolution. We demonstrated for the first time the feasibility of this concept with a prototype version of SI3 fully tested in the laboratory, which was capable of delivering a highly significant zero baseline narrow band measurement of the correlation. Between November 2025 and April 2026 the first three ASTRI SI3 units were successfully integrated on the ASTRI telescopes in Tenerife. Finally, last summer the first on-sky testing and science validation runs were carried out on a sample of brights starts. The full integration and commissioning of the instruments is expected to be completed by the first half of 2027.
