Time-delay interferometry infinity for tilt-to-length noise estimation in LISA

Abstract

The Laser Interferometer Space Antenna (LISA) mission is a space-borne observatory designed to detect and characterize gravitational wave sources inaccessible to ground-based detectors. The mission relies on laser interferometry to measure changes in space-time. In this context, non-avoidable noise sources within the LISA system, including tilt-to-length coupling, reduce the detector's resolution and complicate achieving the mission's goals unless appropriate mitigation strategies are implemented. This paper applies Time-Delay Interferometry Infinity (TDI-∞) for tilt-to-length noise estimation in LISA and assesses its suitability from the perspective of system identification and calibration for the first time. The recently published TDI-∞ concept indicates a different frequency response within the LISA measurement band compared to the standard methodology of TDI second-generation. Our main contribution is demonstrating the advantages of the TDI-∞ algorithm for tilt-to-length noise calibration in space-borne interferometer constellations. Specifically, we show that this algorithm improves the estimation performance of tilt-to-length noise due to its frequency behavior while requiring less computation time. The reduction in computational effort afforded by the TDI-∞ algorithm accelerates the availability of calibrated TDI data for astrophysical analysis if required by the LISA science community. The improvement in estimation performance underscores the concept's potential to enhance the detector's sensitivity further.

The evaluation for plasma noise in arbitrary time-delay interferometry combinations

“…The residual clock noise is 2-3 orders of magnitude larger than the noise floor, and an algorithm has been studied to effectively suppress clock noise [18,28,41,42]. The TTL noise can be mitigated through parameter estimation techniques [43][44][45].…”

“…Currently, we have identified 45 second-generation essential TDI combinations up to sixteen links using geometric approach. The naming of 45 Other TDI combinations can be derived through index permutation and symmetry operation. The specific designations and classifications are published in [33].…”

On point-ahead angle control strategies for TianQin

“…For small jitters near a given angle, the effect can be modeled to the first order by a linear relationship via a set of coupling coefficients (TTL factors) [11]. Due to inevitable misalignment and imperfection of optical components and pointing offsets of laser beams, it is highly challenging to reduce the coupling coefficients to desired small values in hardware, and therefore dedicated TTL factor estimation and noise subtraction in post-processing seem necessary in the current measurement scheme [11][12][13][14]. Unfortunately for various reasons, PAA adjustments are expected to change the TTL factors [7,15].…”