Transient acceleration events in LISA Pathfinder data: properties and possible physical origin

TL;DR

This paper analyzes transient glitches in LISA Pathfinder data, categorizing them into two types, exploring their properties, potential physical origins, and implications for future gravitational wave detector design.

Contribution

It provides a detailed classification and analysis of glitches, identifying likely sources like outgassing, and discusses mitigation strategies for LISA.

Findings

Two distinct glitch categories identified

Outgassing likely source of force glitches

Implications for LISA design and mitigation

Abstract

We present an in depth analysis of the transient events, or glitches, detected at a rate of about one per day in the differential acceleration data of LISA Pathfinder. We show that these glitches fall in two rather distinct categories: fast transients in the interferometric motion readout on one side, and true force transient events on the other. The former are fast and rare in ordinary conditions. The second may last from seconds to hours and constitute the majority of the glitches. We present an analysis of the physical and statistical properties of both categories, including a cross-analysis with other time series like magnetic fields, temperature, and other dynamical variables. Based on these analyses we discuss the possible sources of the force glitches and identify the most likely, among which the outgassing environment surrounding the test-masses stands out. We discuss the impact of these findings on the LISA design and operation, and some risk mitigation measures, including experimental studies that may be conducted on the ground, aimed at clarifying some of the questions left open by our analysis.