LGWA Meeting 2026

28 Sept 2026, 14:00 → 2 Oct 2026, 12:30 Europe/Rome

The Collaboration of the Lunar Gravitational-wave Antenna (LGWA) is inviting to its annual meeting at the University of Liège in Belgium.

The Monday afternoon is dedicated to a closed meeting of the LGWA Steering Committee.

The main scientific program will take place from Tuesday to Thursday covering gravitational-wave science, multi-messenger and multi-band observations, and lunar science.

People are invited to join the field trip on Friday, which is organized separately from the meeting.

The workshop fee is 250€ for people not participating in the social dinner, and 310€ including the social dinner.

Local Organizing Committee

1. Christophe Collette (University of Liège)
2. Mayana Teloi (University of Liège)
3. Nadine Dumont (University of Liège)
4. Damien Libert (University of Liège)
5. Hélène Darimont (University of Liège)

Scientific Organizing Committee

Alessandro Frigeri (INAF-IAPS)
Jan Harms (GSSI)
Joris van Heijningen (VU Amsterdam)
Andrea Maselli (GSSI)
Gianluca Di Rico (INAF Teramo)
Roberto Serafinelli (Diego Portales University)
Paola Severgnini (INAF OABrera)
Morgane Zeoli (UC Louvain)

Monday, 28 September

14:00 → 17:00 Steering Committee

Closed meeting

Convener: Jan Harms (Gran Sasso Science Institute)

Tuesday, 29 September

09:00 → 10:30 Welcome session & intro talks

Convener: Christophe Collette (University of Liège)

09:00 ESA's HRE program and fundamental science opportunities

Speaker: Sébastien Vincent-Bonnieu (ESA)

09:30 Status of the LGWA

Speaker: Jan Harms (Gran Sasso Science Institute)

09:50 Toward better lunar seismic noise measurement with FSS & SPSS

Speaker: Taichi Kawamura (University Paris Cité)

10:10 SILENCE - A deployment and operation study of the LGWA

Speakers: Pascal Kaufmann (ETH Zurich), Vuadens Thubalenkosi (ETH Zurich)

10:30 → 11:00 Coffee break

11:00 → 12:30 Synergy

11:00 Lunar science

Speaker: Ana Plesa (DLR)

11:30 LISA Science

Speaker: Alessandra De Rosa (INAF - IAPS)

11:50 Scientific synergies with the Einstein Telescope

Speaker: Gabriele Perna (KBFI in Tallinn)

12:10 Report from the LGWA Outreach and Communications group

Speaker: Ferdinando Patat (ESO)

12:30 → 14:30 Lunch

14:30 → 16:00 GW Sciences & MMA

14:30 Intermediate-mass black holes in the deci-Hz window: formation, detection, and multiband prospects

Intermediate-mass black holes (IMBHs), with masses between ~100 and 100,000 solar masses, represent a unique yet elusive population of black holes, potentially bridging the gap between stellar-mass and supermassive black holes. For several decades, IMBHs have been investigated through a variety of observational channels, ranging from stellar dynamics in dense star clusters to accretion signatures and tidal disruption events. However, compelling evidence for their existence and, in particular, their formation pathways remains limited.
Gravitational waves offer a new and powerful way to identify and characterize these objects through direct measurements of their masses and spins. Current ground-based detectors probe primarily the lower-mass end of the IMBH spectrum, while future space-based observatories such as the Laser Interferometer Space Antenna (LISA) will access the high-mass end. Deci-Hz interferometers could bridge these regimes, providing sensitivity to a large fraction of the IMBH mass spectrum and potentially enabling truly multiband observations.
In this talk, I will first discuss possible formation pathways for IMBHs, focusing on dense stellar environments where repeated mergers and stellar collisions can drive their hierarchical growth.
I will then discuss the recent observation of GW231123 by the LIGO-Virgo-KAGRA Collaboration. With a component mass in the IMBH regime and remarkably high spins, this event provides an intriguing case study for testing models of IMBH formation and hierarchical growth.
Finally, I will explore the prospects for detecting intermediate-mass-ratio inspirals (IMRIs) across multiple gravitational-wave bands. I will show how deci-Hz observations can significantly expand the population of IMRIs accessible to ground-based detectors and provide a unique opportunity for multiband observations.

Speaker: Lavinia Paiella (GSSI)

15:00 Building Up an Intermediate-Mass Black Hole: The Role of Stellar Collisions

Intermediate-mass black holes (IMBHs, $10^2 < m_{\rm BH}/\mathrm{M}_\odot < 10^5$) populate the poorly constrained mass range between stellar-mass and supermassive black holes. Upcoming gravitational-wave facilities will play a key role in probing this population and its formation channels. In particular, IMBHs and intermediate mass-ratio inspirals involving an IMBH and a stellar-mass compact object will be prime sources for next-generation detectors operating in the deci-Hz band.

Compact, rapidly evolving star clusters are thought to be ideal sites for runaway chains of stellar collisions, forming very massive stars (VMSs, $m_* > 150\,\mathrm{M}_\odot$) that may collapse into IMBHs. However, direct $N$-body simulations remain computationally challenging in these dense environments.

In this talk, I present a complementary semi-analytic approach to this formation channel. I will introduce STARfall, a code that models the dynamical evolution of a massive stellar binary in a cluster core, incorporating prescriptions for cluster evolution, stellar encounters, and collisions.

I will identify the environments that favor runaway collisions and show how repeated mergers drive the growth of VMSs, the masses they can reach, and how stellar winds determine the final IMBH mass. While dynamics governs VMS growth, stellar evolution sets the final IMBH mass. I will finally discuss implications for present-day globular clusters and high-redshift systems in the Cosmic Gems Arc, highlighting where IMBH seeds are most likely to form.

Speaker: Filippo Simonato (Gran Sasso Science Institute)

15:20 Tracing Massive Black Hole evolution with Gravitational Waves and dual AGN

Understanding the formation and evolution of intermediate-mass (IMBH; $10^3 M_\odot < M_\mathrm{BH} < 10^5 M_\odot$) and supermassive black holes (SMBH; $M_\mathrm{BH} ≥ 10^5 M_\odot$) is among the hottest and most challenging open topics in astrophysics. The proposed Lunar Gravitational-wave Antenna (LGWA) will open a new observational window on the mergers of these systems, probing a frequency range complementary to existing (Laser Interferometer Gravitational-Wave Observatory, Virgo, KAGRA and Pulsar Timing Arrays [PTAs]) and planned (Laser Interferometer Space Antenna [LISA] and Einstein Telescope) gravitational-wave observatories. In this talk, I will present a simple framework to predict the population of IMBH binaries detectable by LGWA. Using dark matter-only cosmological simulations from PINOCCHIO code combined with the semi-analytical model PinGAEA, I will present a model to track the separation of MBH pairs starting from megaparsec scales of halo merger down to the galaxy merger and eventually the BH merger. Using this model on both light (~$100 M_\odot$) and heavy ($10^5 M_\odot$) BH seeding schemes, I will create populations of IMBHs and SMBHs pairs which will be used to make predictions for the dual AGN fraction and compare with the latest observational estimates. I will also present the merger rate of these MBH pairs detectable by LGWA and LISA. Finally, I will show the GW background generated by these MBH pairs, and compare with the latest results from PTA experiments.

Speaker: Jasbir Singh (INAF - Osservatorio Astronomico di Brera)

15:40 More Than a Sidekick: Secondary Black Holes in Hierarchical Mergers

Stellar clusters are efficient factories of dynamical interactions and play a crucial role in shaping the black hole (BH) mass distribution accessible to gravitational-wave (GW) observatories. Their ability to retain and repeatedly pair BHs enables the formation of remnants well beyond the pair-instability mass gap, a feature that distinguishes dynamical formation channels from isolated binary evolution. This is highlighted by recent events such as GW231123, possibly the first merger involving an intermediate-mass black hole (IMBH, mass above 100 solar masses), a mass range where decihertz observatories such as LGWA are expected to provide unique sensitivity.
In this work, we investigate the hierarchical assembly of binary BHs, focusing on the formation and evolution of secondary branches within BH merger trees. We introduce a new formalism in our semi-analytical population-synthesis code BPOP to track the growth of structured hierarchical chains. We find that, without these chains, the probability of forming IMBH binaries in the 300–1000 solar mass range, that lies well within the LGWA band, is essentially negligible: hierarchical secondary mergers are the dominant channel populating this mass range, while also leaving distinct signatures in spin. Notably, these systems sit at the interface between the ET and LGWA frequency bands, making them prime candidates for multiband GW observations.
I will present the main results of this work and the merger rates expected for current and next-generation GW observatories, including ET and LGWA. I will show that tracking the full hierarchical structure of secondary mergers is essential to interpret the high-mass tail of the BH population, and that these hierarchical IMBH binaries offer a concrete multiband target linking ET and LGWA science.

Speaker: Cristiano Ugolini (GSSI)

16:00 → 16:30 Coffee break

16:30 → 18:05 GW Sciences & MMA

16:35 Constraining the microphysical properties of neutron stars and white dwarfs with the observation of mergers

Speaker: David Radice (PSU)

17:05 Modeling the local population of double white dwarfs

Speaker: Giovanni Benetti (University of Padova)

17:25 LSST and the role in the identification of LGWA counterparts

Speaker: Silvia Piranomonte (INAF)

17:45 Grawita

Speaker: Maria Grazia Bernardini (INAF)

19:00 → 21:00 Social Event: LGWA stand up show

Stand up by Arnaud Stiepen

Wednesday, 30 September

09:00 → 10:30 Payload

Convener: Joris van Heijningen (VU Amsterdam)

09:00 The payload of the Lunar Gravitational-wave Antenna (session introduction)

Speaker: Joris van Heijningen (VU Amsterdam)

09:10 Cryogenic Interferometric Inertial Sensors for next-generation Gravitational-Wave Detectors

The Lunar Gravitational-wave Antenna payload will be composed of an array of seismic stations in a permanently shadowed crater. Highly sensitive cryogenic inertial sensors will be deployed at seismic stations to detect the difference between the elastic response of the Moon and the motion of the suspended inertial sensor proof mass induced by gravitational waves. This talk presents the first experimental validation of a vertical and a horizontal interferometric inertial sensor designed for operation in low vibration cryogenic environments relevant to next generation gravitational-wave detectors such as the ET-LF and the LGWA. The sensor targets 10 fm/√Hz displacement sensitivity from 2-3 Hz, while operating at temperatures down to a few kelvin. We report on the characterization of key subsystems under cryogenic conditions, including the interferometric readout, suspensions, and mechanics. The homodyne quadrature interferometric readout achieves sub picometer resolution above 0.4Hz at 17K, with performance limited by shot noise at higher frequencies and temperature fluctuations at low frequencies. The sensors are then characterized in a dedicated low-vibration cryogenic environment to demonstrate their operation at temperatures down to 5.12K. These results confirm the operation and robustness of interferometric inertial sensing at cryogenic temperatures, and set the building blocks for LGWA soundcheck.

Speaker: Morgane Zeoli (Université Catholique de Louvain-la-Neuve)

09:30 Design and Numerical Modeling of a Breadboard Leveling Platform for the LGWA Mission

The main goal of the LGWA mission is to observe and monitor gravitational-wave (GW) signals. One of the key technologies employed for this purpose is the inverted pendulum suspension, whose low resonance frequency provides the mechanical sensitivity needed to detect the extremely faint surface displacements induced by GWs. However, because this suspension is extremely soft, the sensor becomes highly susceptible to tilt-to-horizontal coupling small deviations in ground orientation are readily misread as horizontal displacement. For this reason, a leveling mechanism is required to establish and maintain the correct orientation of the seismic station relative to local gravity, keeping the ground-mounted instrument level despite lunar terrain and settling effects. Each LGWA station platform must be leveled to an accuracy of a few tens of microradians to ensure optimal functionality of the Lunar Inertial Gravitational-wave Sensors (LIGS). Previous research on this subsystem has primarily addressed basic design concepts, constraints, and feasibility considerations. Building on this foundation, the objective of this work is to develop, through numerical simulation and CAD-based modeling, a breadboard-level leveling mechanism, and subsequently validate it experimentally. The expected outcome of this work is a numerically validated breadboard-level leveling mechanism model demonstrating stable operation under low-temperature conditions, as well as a suitable frequency response avoiding the mode region relevant to LGWA's measurement band, providing a basis for future scaling toward flight-relevant dimensions.

Speaker: Veronika Glazkova (GRAN SASSO SCIENCE INSTITUTE)

09:50 Development of a Moon Emulator for the Lunar Gravitational-Wave Antenna (LGWA)

The Lunar Gravitational-Wave Antenna (LGWA). The development of such a mission requires the qualification of seismometers and other cryogenic technologies under representative lunar conditions. To support this effort, a laboratory-scale Moon Emulator is being developed to reproduce high-vacuum and cryogenic environments for testing and validation.
As part of this project, the presented work focuses on the design of the cryogenic vacuum chamber that’s the interface between the cryocooler and the main experimental chamber. The chamber is being developed to provide a modular and maintainable platform for suspended thermal links and future experimental payloads while ensuring compatibility with cryogenic operation and high-vacuum requirements. Particular attention is given to mechanical stability, accessibility, and future integration with the complete Moon Emulator.
The current work is in the design phase. Future activities will include structural and thermal analyses, fabrication, and experimental validation, contributing to the development of technologies required for the LGWA mission.

Speaker: Tarun Singh (Gran Sasso Science Institute, L'aquila, Italy)

10:10 LGWA Soundcheck E-Box. Requirements, Design and Legacy from the Insight E-Box

We present a preliminary assessment of the required and expected performances for the LGWA Soundcheck sensor acquisition electronics (LGWA Soundcheck E-Box). The most stringent requirements come from sensing noise performances and power consumption. We discuss the current assumptions and the projected performances based on the legacy from the Insight E-Box and the LISA Pathfinder GRS FEE. The current analysis shows we are able to deliver noise performances well below 1 uV/Hz^(1/2), corresponding to ~1 pm/Hz^(1/2) in the frequency band of interest for LGWA Soundcheck. The projected power consumption is expected to be below 4-5 W during science operations.

Speaker: Luigi Ferraioli (ETH Zurich)

10:30 → 11:00 Coffee break

11:00 → 12:30 GW Sciences & MMA

11:00 Stochastic backgrounds of gravitational waves (also) in the deciHz band

Speaker: Angelo Ricciardone (University of Pisa)

11:30 Extreme and intermediate mass-ratio inspirals

online

Speaker: Chris Berry (University of Glasgow)

11:50 Gravitational-wave parameter estimation to the Moon and back: synergies between ground and LGWA for BBHs

LGWA will expand our observational reach and help us access new sources of GWs. At the same time, third-generation (3G) gravitational-wave (GW) detectors will usher GW science into the big-data era, with tens to hundreds of thousands of detections each year. In this talk, I will discuss the complementarity of ground-based detectors and LGWA, with a focus on the multiband observation potential for binary black holes (BBHs).

I will present an assessment of the detectability for BBH populations consistent with the latest LIGO–Virgo–KAGRA reconstruction. LGWA alone could have observed more than one-third of the events detected through GWTC-4.0, and could detect 90 events per year merging in the ground-based band out to redshifts $z\sim3-5$. Current detectors at design sensitivity would yield one to a few hundred multiband counterparts with LGWA. In contrast, 3G detectors could observe most BBHs detected by LGWA that merge in their frequency band ($7\,M_\odot$ ≲ $M_{\rm tot}$ ≲ $600\,M_\odot$), enabling systematic joint analyses of hundreds of events.

The short time to merger from the deci-Hz to Hz–kHz band (typically months to a year) enables early warning, targeted follow-up, and archival searches. I will highlight the promising case of intermediate-mass BBHs, presenting an injection study for a GW231123-like system that accumulates $\sim10^5$ inspiral cycles in LGWA. I will further discuss some parameters for which LGWA can deliver an exquisite reconstruction.

Speaker: Francesco Iacovelli (Johns Hopkins University)

12:10 Applying the LISA Science Ground Segment Model to the Lunar Gravitational-wave Antenna

The Lunar Gravitational-wave Antenna (LGWA) mission aims to deploy a network of highly sensitive inertial sensors on the Moon, providing unprecedented observations in the decihertz gravitational-wave band. To successfully manage the data flow and fully exploit the scientific capabilities of the mission, a robust and distributed Science Ground Segment (SGS) must be designed from the earliest phases of the mission, capable of transforming raw telemetry into calibrated data products, science-ready observables, and public data releases while supporting mission operations throughout the lifetime of the observatory. This presentation proposes a conceptual architecture for the LGWA SGS, describing its main functional components and its interfaces with mission and instrument operations, using the LISA SGS model — currently under active development and testing — as a reference.

We outline a distributed processing approach, following the model adopted by medium-to-large missions such as Euclid and LISA, in which the Science Operations Centre is responsible for telemetry processing, mission archiving, quick-look analysis for instrument health checks, and low-latency pipelines up to Level 1 data products. Higher-level scientific processing is instead performed by the Consortium through Distributed Science Data Centres (DSDCs) coordinated via a central software repository. This distributed network is responsible for generating Level 2 data products (e.g. model parameters and posterior probability density functions of identified GW sources) as well as Level 3 products (source catalogues, with their physical and astrophysical parameters). The DSDCs are also expected to support end-to-end mission simulations, used both to validate the processing pipelines and to characterise instrument response, as well as long-term monitoring of instrument performance to track detector health and calibration stability over the mission lifetime.

Finally, we discuss the common infrastructure required to support the SGS, including the definition of a shared Data Model for all the SGS data products, the Mission Database, containing mission configuration, constants and calibration information, a common workflow management system to execute and distribute data processing pipelines, and distributed storage solutions. Central to this infrastructure is a container-based software deployment strategy, designed to seamlessly support not only the mission’s data production system but also a prototyping environment, where the Science Team and the DSDC teams can collaboratively develop, test, and validate data analysis pipelines before deployment. We also present the adoption of cloud-native open-source technologies as a foundation for these services, enabling a modular, reproducible, and collaborative infrastructure that can support the long-term evolution of the LGWA mission.

Speaker: Marco Frailis (INAF-Astronomical Observatory of Trieste)

12:30 → 14:30 Lunch

14:30 → 16:00 Payload

14:30 NbN Superconducting Coil Platform for Cryogenic Sensing and Actuation

Next-generation gravitational wave observatories operating at cryogenic temperatures demand advanced sensing and actuation platforms with minimal thermal noise and power dissipation. While superconducting systems have historically relied on wirewound coils operated at liquid helium temperatures, higher operating temperatures necessitate superconductors with elevated critical temperatures. We present a thin-film engineering approach to superconducting coils based on niobium nitride (NbN), a material system that enables device geometries unattainable through conventional wire-winding techniques. Our 200 nm thick NbN coils, fabricated on single-crystal MgO substrates, demonstrate sharp superconducting transitions with a critical temperature of 14.4 K and critical currents exceeding 180 mA, sufficient to sustain ampere- level persistent currents. The coils exhibit excellent mechanical stability under repeated thermal cycling, with optimized geometries featuring enlarged contact pads ensuring robust performance. Numerical and analytical simulations confirm that these coils generate sub-micronewton forces at 0.1 mm separation distances, substantially exceeding the nanonewton-scale actuation requirements for mirror suspension in gravitational wave detectors. These results establish thin-film NbN superconductors as a viable platform for precision cryogenic
sensing and actuation in the next-generation observatories.

References:
1) Sharma, M., Singh, M., Rakshit, R. K., Singh, S. P., Fretto, M., De Leo, N., & Pinto, N.
(2022). Complex phase-fluctuation effects correlated with granularity in
superconducting NbN nanofilms. Nanomaterials, 12(23), 4109.
2) Van Heijningen, J. V., et al. "The payload of the Lunar Gravitational-wave
Antenna." Journal of Applied Physics 133.24 (2023).
3) Ellenbroek, V. J., Sharma, M., Singh, S. P., Zeoli, M., Gatti, A., Collette, C., & Van
Heijningen, J. V. (2026, February). Design and manufacturing of superconducting coils
for cryogenic (inertial) sensing and actuation. In Journal of Physics: Conference
Series (Vol. 3177, No. 1, p. 012102). IOP Publishing.
4) Cooper, S. J., Collins, C. J., Green, A. C., Hoyland, D., Speake, C. C., Freise, A., &
Mow-Lowry, C. M. (2018). A compact, large-range interferometer for precision
measurement and inertial sensing. Classical and Quantum Gravity, 35(9), 095007.
5) Ferreira, E. C., Bocchese, F., Badaracco, F., van Heijningen, J. V., Lucas, S., & Perali,
A. (2021, December). Superconducting thin film spiral coils as low-noise cryogenic
actuators. In J. Phys. Conf. Ser (Vol. 2156, p. 012080).
6) Blair, C., Gras, S., Abbott, R., Aston, S., Betzwieser, J., Blair, D., & Romie, J. H. (2017).
First demonstration of electrostatic damping of parametric instability at advanced
ligo. Physical review letters, 118(15), 151102.

Speaker: Meenakshi Sharma (CPFS)

14:50 Latest results on numerical superconducting coil simulations

Improving the inertial sensitivity of the Lunar Gravitational Wave Antenna (LGWA) directly enhances its detection sensitivity. By exploiting the Meissner effect, superconducting thin-film dual-coil designs enable sub-femtometer precision sensing and high-precision actuation with negligible heat dissipation, thereby reducing required cooling capacity, radiator area, total weight, and mission costs. We present a deposition-based design methodology for thin-film coils compatible with higher operating temperatures than conventional wirewound coils, offering greater flexibility for LGWA's operating temperature range. Fabricated niobium nitride (NbN) coils achieved a critical temperature of 15.6 K and demonstrated persistent currents scalable up to the ampere-level in thin films. COMSOL-optimized designs confirm that the actuator coils can exert sub-micronewton forces on a superconducting surface fully maintained in the Meissner state, while the sensor coils generate the expected signal currents required to achieve sub-femtometer sensitivity. These results demonstrate the feasibility of a new generation of superconducting sensing and actuation solutions.

Speaker: Veerle Ellenbroek (VU Amsterdam)

15:10 A Superconducting Resonant LC Displacement Sensor using a Digital Phase-Locked Loop

A design is presented for a superconducting displacement sensor which could provide an alternative approach to the persistent current sensing scheme for the LGWA. The sensor is predicted to give a displacement sensitivity better than 1 fm Hz-1/2 over a frequency range from mHz up to kHz, with a working range of order 1 mm, without injecting heat or significant mechanical noise into the system. The basis of the measurement protocol is to use a digital Lock-In Amplifier (LIA) drive a high-Q (the target Q is about 106) superconducting LC circuit at its resonance at a frequency of around 5 MHz, producing a large current which can the be measured precisely with a two-stage SQUID. The sensing coil in the superconducting LC circuit is coupled to the test mass whose displacement is to be sensed. The motion of the test-mass modulates the inductance of the circuit, which changes its resonant frequency. Because of the high Q of the circuit, this produces a large change in the phase of the current measured by the DC SQUID. This measured signal is then fed back to to the LIA and the frequency is adjusted to be at the new resonant frequency of the LC circuit.

The displacement is therefore read out using the resonant frequency of a superconducting circuit, rather than the amplitude of the signal, and so the signal is largely insensitive to stray capacitance and inductance of the cables. Avoiding the requirement for persistent currents means that the circuit is easier to implement with thin-film superconductors such as NbN and NbTiN, so can be implemented at higher temperature.

Beyond this target application, the sensor could be applied in many other fields, such as inertial sensors for terrestrial gravitational wave detectors, gravity gradiometry, geophysics, and lunar and solar system planetary exploration. We aim to demonstrate the measurement principle, first using a room temperature version of the circuit, then with lithographically produced superconducting coils and capacitors, and to use a quiet cryogenic platform to demonstrate that we can reach the target sensitivity.

Speaker: Christopher Collins (Nikhef)

15:30 Lunar silicon cavity

online

Speaker: Jun Ye (JILA, NIST, University of Colorado)

16:00 → 18:00 Visit of the Etest prototype at the Liège Space centre

Located at the Space Center of Liège in the Liège Science Park, Belgium, the CRyogenics and Inertial STAbility Laboratory ET-CRISTAL is an open living laboratory dedicated to the validation of key technologies necessary for the future Einstein Telescope.
It consists of a full scale prototype mirror, isolated from seismic motion at low frequency, and cooled down at cryogenic temperature using purely radiative technology.

19:00 → 23:00 Social dinner

The social dinner will take place in a typical Belgian 'brasserie' located in the historic city centre.

Thursday, 1 October

09:00 → 10:30 Industry

09:00 SONACA

09:30 Space Applications Services

10:00 Redwire - Building a sustainable base on the Moon

Speaker: Mr Frank Preud'homme

10:30 → 11:00 Coffee break

11:00 → 12:30 Technology panel discussion

12:30 → 14:30 Lunch

14:30 → 16:00 Site & Lunar science

14:30 Modeling the Lunar Response to GWs in the Era of China’s Chang’E Mission

Speaker: Xian Chen (Peking University)

15:00 Gravitational-wave Tomography of the Moon: Constraining Lunar Structure with Calibrated Gravitational Waves

The recent success of gravitational-wave (GW) astronomy together with renewed plans for lunar geophysical instrumentation has revived interest in using the Moon as a resonant detector for mid-frequency (mHz-Hz) GWs. In realistic observational scenarios, the GW strain amplitude is expected to be constrained independently by networks of GW detectors, which motivates an inverse, tomographic question: to what extent can measurements of the Moon's seismic response to known GWs be used to infer its internal structure? In this work, we develop a first-principles, perturbative framework that maps spherically symmetric perturbations of the elastic and density structure to measurable changes in observables, especially GW-driven modal amplitudes of the Moon. The formalism combines (i) a normal-mode representation of the elastic response, (ii) first-order perturbation theory for eigenvalues and eigenfunctions, and (iii) a linearized observation model that links frequency and amplitude observables to model parameters (bulk and shear moduli, density, and interface locations) and their perturbations. We show that the estimation errors of the Moon's elastic parameters can be reduced by about an order of magnitude with observations of calibrated GWs.

Speaker: Han Yan (Peking University)

15:30 The lunar science case of Soundcheck (t.b.c.)

16:00 → 16:30 Coffee break

16:30 → 18:00 Discussion: LGWA activities in the next year and beyond

Convener: Jan Harms (Gran Sasso Science Institute)

18:00 → 20:00 Social Event: Belgian beer degustation

We are inviting you to attend a special belgian beer degustation

Friday, 2 October

09:00 → 12:00 Field trip

Convener: Christophe Collette (University of Liège)