The Lunar Gravitational-wave Antenna: Mission Studies and Science Case

TL;DR

LGWA proposes a planetary-scale decihertz gravitational-wave detector on the Moon, deploying an array of inertial sensors to observe GWs in the 1 mHz–1 Hz band and bridging LISA with future terrestrial detectors. The paper analyzes mission concepts, instrument noise budgets, seismic-background reduction, lunar GW response, calibration, and sensitivity models, and outlines forthcoming upgrades. It presents a broad science case spanning lunar seismology, internal structure, and formation history, as well as GW astrophysics, cosmology, and fundamental physics, including multiband observations with LISA and 3G detectors. Beyond GW science, LGWA aims to open lunar science opportunities through extensive studies of the surface environment, regolith, and tectonic processes, leveraging pathfinder data from Soundcheck and upcoming lunar missions. Overall, LGWA offers unique, long-baseline GW access in the decihertz regime, enabling early warnings for compact binaries, probing IMBH/MBH populations, testing gravity, and delivering novel lunar interior and geophysics insights. The mission plan emphasizes readiness activities, cross-disciplinary impact, and the potential for a durable lunar GW detector network.

Abstract

The Lunar Gravitational-wave Antenna (LGWA) is a proposed array of next-generation inertial sensors to monitor the response of the Moon to gravitational waves (GWs). Given the size of the Moon and the expected noise produced by the lunar seismic background, the LGWA would be able to observe GWs from about 1 mHz to 1 Hz. This would make the LGWA the missing link between space-borne detectors like LISA with peak sensitivities around a few millihertz and proposed future terrestrial detectors like Einstein Telescope or Cosmic Explorer. In this article, we provide a first comprehensive analysis of the LGWA science case including its multi-messenger aspects and lunar science with LGWA data. We also describe the scientific analyses of the Moon required to plan the LGWA mission.

Figures (33)

• Figure 1: Conceptual overview of an LGWA seismic station on a tilted surface on the lunar regolith. The roughness and tilt of the lunar surface are exaggerated for illustrative purposes. Several subsystems vital to successful operation are depicted and further detailed in the text. Subsystems are not shown to scale. Figure adjusted from vHeEA2023.
• Figure 2: Minimum detectable inertial displacement for the two LGWA concepts: \ref{['sfig:NbIFO']} a niobium Watt's linkage with laser-interferometric readout and \ref{['sfig:SiSQUID']} a silicon Watt's linkage with superconductive readout. All readout noises are corrected by the mechanical transfer function of the proof mass suspension.
• Figure 3: Modeling of the lunar GW response in the decihertz band requires analytical studies and numerical simulations based on a geological and topographic model of the deployment site. Gravitational waves generate seismic waves propagating in normal direction to the surface and interfaces.
• Figure 4: Models of characteristic strain sensitivities.
• Figure 5: Left: LGWA horizon for equal-mass black hole binaries, compared to Einstein Telescope and LISA. The mass value is given in the source frame. Right: Redshift threshold for detection (SNR$\> 15)$ for an IMRI with primary mass $M_{\rm IMBH}$ and secondary mass of $30 M_{\odot}$. The central blue region corresponds to LGWA, which can be compared with the horizons of the Einstein Telescope (left region, green) and LISA (right region, red).