Sourath Tarun Ghosh

Laser Interferometer Space Antenna (LISA) will be the first gravitational wave (GW) detector to be sensitive to sources radiating at milli-hertz frequencies. The science goal also makes it the first space-based GW detector with a unique interferometer design that entails 2.5 million kilometer arms oriented in a triangular configuration with a picometer-level optical pathlength stability requirement. LISA passed the critical mission adoption phase in 2024 with the primary science goals and the final interferometer design described in the LISA definition study report. The bulk of my Ph.D. entails two very distinct projects, both probing aspects beyond the established instrument design and science goals. The first project, arm locking, explores the idea of an onboard laser frequency noise suppression scheme that uses LISA arms as a frequency reference. The improved onboard laser frequency noise would provide risk mitigation for implementing Time-Delay Interferometry, a critical post processing step to produce science data streams. The second project aims to add to LISA's science goals by developing an algorithm that looks for displacement gravitational wave memory (GW memory) of LIGO binaries in LISA data. Individual GW memory signals are not detectable. Our algorithm involves using information from ground-based detector catalogs to coherently stack LISA data corresponding to these events. In this talk, I will start with a brief summary of LISA. Following this, I will describe my work on the aforementioned projects in detail.