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GR: Fachverband Gravitation und Relativitätstheorie

GR 16: Gravitational Waves I

GR 16.1: Talk

Thursday, March 14, 2024, 14:45–15:05, HBR 14: HS 2

Intersatellite Ranging and Clock Synchronization for the Laser Interferometer Space Antenna — •Jan Niklas Reinhardt — Max-Planck-Institut für Gravitationsphysik, Callinstraße 38, 30167 Hannover

Ground-based gravitational wave detectors are blind below 10 Hz due to gravity gradient noise, etc. The Laser Interferometer Space Antenna (LISA) avoids these difficulties by going to space. Hence, it extends gravitational wave astronomy to the sub-hertz frequency band. LISA consists of 3 satellites in a triangular constellation trailing Earth by 20 degrees on its orbit around the sun. Gravitational waves cause pico meter variations in the 2.5 million km arm lengths. To detect them the satellites are connected by six infrared laser links, and heterodyne interferometry is performed between received and local lasers, respectively. The LISA measurements are swamped by laser frequency noise. An on-ground data processing technique called time-delay interferometry (TDI) is applied, which combines the beatnotes from the different satellites with the correct delays to virtually form equal-optical-path-length interferometers, in which laser frequency noise naturally cancels. To obtain the required delays, we combine the four LISA ranging observables in a ranging sensor fusion: PRN ranging, ranging information from the clock sideband beatnotes, TDI ranging, ground-based observations. Each satellite has its own on-board timer. We combine the intersatellite ranges with ground observations to estimate their desynchronisations from the barycentric coordinate time (TCB). Hence, we synchronize the on-board timers to TCB.

Keywords: Gravitationswellen; Laser Interferometer Space Antenna; LISA Data Processing; Intersatellite Ranging and Clock Synchronization