Improving LIGO calibration accuracy by tracking and compensating for slow temporal variations

TL;DR

This paper presents a method to improve LIGO calibration accuracy by tracking slow temporal variations in the detectors' response using injected modulations, leading to reduced systematic errors.

Contribution

The paper introduces a calibration technique that accounts for slow parameter variations in LIGO detectors, enhancing measurement precision.

Findings

Significant reduction in systematic calibration errors.

Effective tracking of slow temporal variations.

Improved calibration accuracy demonstrated on LIGO detectors.

Abstract

Calibration of the second-generation LIGO interferometric gravitational-wave detectors employs a method that uses injected periodic modulations to track and compensate for slow temporal variations in the differential length response of the instruments. These detectors utilize feedback control loops to maintain resonance conditions by suppressing differential arm length variations. We describe how the sensing and actuation functions of these servo loops are parameterized and how the slow variations in these parameters are quantified using the injected modulations. We report the results of applying this method to the LIGO detectors and show that it significantly reduces systematic errors in their calibrated outputs.