Gravitational-wave astronomy with a space-based optical clock network

Since the first detection of a merging binary black hole system a decade ago, gravitational-wave astronomy has emerged as a powerful tool for astrophysics. Future space-based observatories, such as the Laser Interferometer Space Antenna (LISA), will unlock the millihertz (mHz) band, which remains entirely inaccessible to ground-based detectors due to terrestrial noise. In parallel, proposed atom-based gravitational-wave detectors, specifically those based on space-based optical clocks and atom interferometers, offer capabilities that are unique and complementary to traditional optical interferometers. Their highly tunable character enables sensitive measurements across a broad frequency band extending from the mHz up to and possibly even above the Hz regime. In this work, we investigate the use of one-way Doppler tracking in space-based atomic clock networks operating in concert with detectors like LISA. We analyze the dominant noise sources and develop dedicated measurement protocols, which operate in a targeted mode, using an externally supplied signal model to track the response coherently as the source chirps. Performing preliminary parameter estimation on simulated signals, we demonstrate how these detectors could be used to extract critical astrophysical information about binary gravitational-wave sources. We further show that the same instrument retains sensitivity in a search mode, where no prior on the source is assumed.