Detection and characterization of gravitational wave signals with an astrometric antenna in space

Since the first detection of gravitational waves, continuous efforts in experimental gravitation have focused on advancing current and future detectors to expand the observable frequency range, enhance source parameter estimation, and refine sky localization. In such a context, the Astrometric Gravitational Wave Antenna (AstroGraWAnt) stands as an astrometric mission concept specifically designed for gravitational wave detection. It consists of a space-borne antenna equipped with a minimum of three lines of sight, which exploits the strengths of differential astrometry within a fully relativistic framework to enhance the astrometric response to gravitational waves. In this thesis we evaluate the observational principles of AstroGraWAnt along with its performance as a gravitational wave detector. We investigate the instrument’s response to representative astrophysical sources, including extragalactic compact binary coalescences and binary systems in the Milky Way. The latter offers a much more promising detection scenario thanks to the coherent integration of monochromatic signal over years of observations. We then derive the directional antenna response and compare it with both ground-based and space-borne interferometers. The analysis indicates that AstroGraWAnt offers a highly isotropic sky coverage. Finally, we define the sensitivity frequency range of AstroGraWAnt, which results remarkably broad, from 10−8Hz to 0.1Hz. Afterwards, we introduce some noise components, such as white noise, broad-band contributions and line features, to define a preliminary sensitivity curve accessible to the mission. By defining key features and operational scenarios, this thesis paves the way for the development of AstroGraWAnt, proving the potential of dedicated space astrometry as a novel frontier for gravitational wave astronomy