Pattern functions of the Astrometric Gravitational Wave Antenna

Since the first detection of gravitational waves (GWs), the field of experimental gravitation is steadily working on improving the current detectors as well as developing new instruments in order to expand the range of observable frequencies and improve the reconstruction of the GW direction and source parameters. In such a context, the Astrometric GW Antenna, consisting of at least three pairs of lines of sight assembled in a very compact configuration, represents a promising concept to achieve the above goals. Therefore, its detection capabilities and performances should be characterised. We derive the pattern functions of the Astrometric GW Antenna to estimate its directional response, allowing initial comparisons with other detectors and among different configurations. Our analysis shows that the Astrometric GW Antenna is almost equally sensitive to GWs coming from any direction, and better suited for detecting relatively nearby events. The implication is that the Astrometric GW Antenna can be an optimal detector for GW sources located within our Galaxy and can boost the instantaneous sky coverage of current ground-based interferometers. Moreover, the complementarity with the observations of LISA space antenna is emphasised. Finally, the detection range can be further expanded by combining simultaneous observations of a few replicas of the Astrometric GW Antenna.