Between 2015 and 2017, the technology demonstrator LISA Pathfinder paved the way for the first gravitational wave observatory in space: the Laser Interferometer Space Antenna (LISA). LISA Pathfinder successfully demonstrated the working principle of the future LISA mission and provided a test assembly for the analysis of various residual noise sources. A crucial noise source was the cross-coupling of lateral and angular spacecraft jitter into the main scientific readout signal. We refer to this noise as Tilt-To-Length (TTL) coupling. In LISA Pathfinder, it was visible as access noise between 20 and 200mHz and removed by subtraction in post-processing. TTL coupling is also expected to be a major noise source in the LISA mission.
In this talk, I will present our analysis of the TTL coupling in LISA Pathfinder. We studied the coupling for a cross-coupling experiment using a new analytical and a fit model. Thereby, we show that both can successfully subtract the coupling noise. Moreover, these models can be used for a physical interpretation of the coupling mechanisms and to mitigate the TTL noise by alignment. Our analysis also revealed scenarios of non-linear TTL coupling. We further investigate the long-term behavior of the TTL coupling coefficients and their dependency on environmental changes.
The subtraction of TTL coupling in post-processing, as well as its direct reduction by realignment, are planned for LISA. Therefore, several of our findings and challenges can become relevant in the TTL data analysis and suppression of the LISA mission.
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Meeting ID: 891 5469 2428
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