Detecting an anisotropic gravitational wave background with a space-borne interferometer

The configuration of a space-borne interferometer is kept stable thanks to the careful design of the orbit of the laser-bearing spacecraft. This complex orbital motion introduces low-frequency amplitude and phase modulations in the response of the detectors. As a consequence, any anisotropic gravitational wave background is seen by these antennas as a non-stationary stochastic signal. In this work, we suggest exploiting this non-stationary characteristic for detecting and measuring the gravitational background generated by an anisotropic population of sources. In particular, in the low-frequency region accessible to space-borne detectors, a major role is played by the Galactic binaries confusion limit, which can be considered as an effective sensitivity limit at frequencies below 3 mHz. Detecting this particular background would therefore provide valuable information about the spatial distribution of sources in our Galaxy.