TDI noises transfer functions for LISA

TL;DR

This paper develops transfer functions for TDI noises in the LISA gravitational wave observatory, enabling accurate noise modeling and performance estimation crucial for data analysis and instrument design.

Contribution

It introduces a methodology to derive TDI noise transfer functions, including models and verification procedures, now used in LISA's performance and noise analysis.

Findings

Transfer functions enable realistic noise modeling.

Application to various configurations improves instrument design.

Supports data analysis with accurate noise curves.

Abstract

The LISA mission is the future space-based gravitational wave (GW) observatory of the European Space Agency. It is formed by 3 spacecraft exchanging laser beams in order to form multiple real and virtual interferometers. The data streams to be used in order to extract the large number and variety of GW sources are Time-Delay Interferometry (TDI) data. One important processing to produce these data is the TDI on-ground processing which recombines multiple interferometric on-board measurements to remove certain noise sources from the data such as laser frequency noise or spacecraft jitter. The LISA noise budget is therefore expressed at the TDI level in order to account for the different TDI transfer functions applied for each noise source and thus estimate their real weight on mission performance. In order to derive a usable form of these transfer functions, a model of the beams, the measurements, and TDI have been developed, and several approximation have been made. A methodology for such a derivation has been established, as well as verification procedures. It results in a set of transfer functions, which are now used by the LISA project, in particular in its performance model. Using these transfer functions, realistic noise curves for various instrumental configurations are provided to data analysis algorithms and used for instrument design.