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Abstract

The LISA mission aims to detect millihertz gravitational waves in space, to observe interesting cosmological and astrophysical sources. Test masses within the three spacecraft provide inertial reference frames, with respect to which length changes are tracked. Dynamical jitters could couple into this measurement, limiting detection. This thesis provides a time-varying, non-linear implementation of the spacecraft dynamics in a control loop, which is thoroughly analysed for strengths of individual components and sensitivity to noise levels. The simulation is also used to demonstrate dynamics noise suppression after post-processing with time-delay interferometry (TDI). Tilt-To-Length (TTL) coupling in LISA describes the coupling of rotational degrees of freedom of spacecraft and optical assemblies into the longitudinal interferometric measurement. The detailed jitters produced by the dynamics simulation are then used to compute the TTL coupling impact on the interferometric output. This is shown to be limited given current estimates on the size of the coupling coefficients, contrary to the expectation that this effect is one of the dominant noise contributions after TDI. Inference using a Least Squares estimator is investigated in many scenarios, including deliberate excitations for improved estimation, based on published designs. To counter a divergence in the limit of zero sensing noise, a regularization term is introduced for the estimator. Using the excitations, the coupling coefficients can be inferred with high accuracy and shorter data durations. Thus, this thesis provides validations for the measurement design of LISA with respect to system dynamics, with detailed analyses of the simulation outputs, and an investigation into the impacts of TTL coupling given the detailed dynamics simulation. This is limited by the final design decisions of the industry contractors, which may differ from the choices made here. Future works can use the simulator to investigate TTL coupling effects in the test mass interferometer, and study the variation of dynamics noises and TTL coupling over the whole mission duration.