Advanced gravitational waves detector CALibration for accurate COsmology – ACALCO

The first new measurement of the Hubble constant (H0) using gravitational waves has been made in 2017. The upcoming data taking of the upgraded LIGO and Virgo detectors should bring results of astrophysical relevance for H0, at the condition that significant progresses are made with the detectors calibration. The ACALCO project objective is to do this R&D to reach a sub-percent absolute calibration uncertainty of the Virgo detector by 2025. The plan is to pursue a combined approach. On the one hand, develop a new calibration system based on the generation of a variable Newtonian gravitational field produced by rotating masses. This technique has been recently explored and could become the new absolute calibration reference. On the other hand, improve the technique which uses the radiation pressure of an auxiliary laser whose power is modulated, to use it as an accurate cross reference and as a system to extend the calibration the whole Virgo detector frequency band.