Future space-based heterodyne interferometry: overcoming limitations in astronomical observations

Space-based long-baseline stellar interferometry has been envisioned for decades because it can bypass atmospheric disturbance and enable significant array scalability with high spectral and angular resolution. However, technological challenges have so far prevented the realization of these missions. The GLORIA project, a collaboration between the German Aerospace Center (DLR) and the Leibniz Institute for Astrophysics Potsdam (AIP), aims to advance the transition of near-infrared (NIR) stellar interferometry from ground-based to space-based observations. This initiative utilizes heterodyne interferometry to digitize delay lines, addressing the limitation of conventional mechanical rail systems used in ground-based interferometers to compensate for optical path differences necessary for achieving interference, which are impractical for space applications. By mixing NIR stellar radiation with a stable reference laser, the project intends to convert the signal into the radio regime, enabling delay line digitization while preserving crucial phase information essential for stellar image reconstruction. The first phase of the ground-testbed aims to establish a controlled testbed environment for tests of heterodyne interferometry. The second phase intends to simulate and measure astronomical conditions, leveraging the phase 1 setup adapted to replicate the complexities of a real stellar interferometer. The current progress of the testbed includes control over phase and amplitude for interferometric measurements with initial characterization of the heterodyne signal.