Validating gravitational-wave detections: The Advanced LIGO hardware injection system

TL;DR

This paper describes the hardware injection system in LIGO, which physically simulates gravitational-wave signals to test and validate the detectors' ability to observe and analyze such signals accurately.

Contribution

It introduces the hardware injection system and demonstrates its use in validating LIGO's detection and analysis capabilities across various simulated gravitational-wave signals.

Findings

Successful recovery of injected signals from binary black hole mergers

Validation of analysis pipelines with hardware injections

Characterization of instrumental subsystem coupling

Abstract

Hardware injections are simulated gravitational-wave signals added to the Laser Interferometer Gravitational-wave Observatory (LIGO). The detectors' test masses are physically displaced by an actuator in order to simulate the effects of a gravitational wave. The simulated signal initiates a control-system response which mimics that of a true gravitational wave. This provides an end-to-end test of LIGO's ability to observe gravitational waves. The gravitational-wave analyses used to detect and characterize signals are exercised with hardware injections. By looking for discrepancies between the injected and recovered signals, we are able to characterize the performance of analyses and the coupling of instrumental subsystems to the detectors' output channels. This paper describes the hardware injection system and the recovery of injected signals representing binary black hole mergers, a stochastic gravitational wave background, spinning neutron stars, and sine-Gaussians.