European Collaboration for Lunar Investigation with Planetary Seismology and Electromagnetism (ECLIPSE): A European Initiative to Strengthen the International Lunar Seismic Network

Introduction:

In response to the exploratory call for missions within ESA’s science program, we propose the ECLIPSE mission to deploy a European geophysical station with seismometers and electromagnetic sensors on the lunar surface. Although data from the Apollo seismic network and subsequent geodetic studies provided initial models of the Moon's internal structure, its interior remains highly complex and not yet well understood. Numerous missions are being planned, with the aim of establishing permanent lunar bases. In this context, lunar seismology is of critical importance, and recent milestones—such as China’s Chang’e missions and India’s Chandrayaan-3—mark the beginning of a new era in lunar seismic exploration. NASA’s Farside Seismic Suite (FSS), part of the CLPS CP-12 flight, is set to perform the first seismic measurements on the Moon’s far side, while the Lunar Environment Monitoring Station (LEMS), included in Artemis 3, will deploy the first human-operated seismometer since Apollo. Meanwhile, China is preparing to send a seismometer aboard Chang’e 7 and later Chang’e 8. These efforts will lay the groundwork for an international lunar seismic network over the next decade.

ECLIPSE aims to set up a European seismic station by deploying a three-axis seismometer on the lunar surface. The vertical axis will feature the last available unit of the Very Broad Band vertical (VBBZ) seismometer — the most sensitive flight-ready seismometer ever built — previously flown on InSight [1], and in preparation for FSS [2]. The horizontal components will consist of two geophones. The seismic suite will be complemented by a radiometer, magnetometer, electric field sensor, short period vertical geophone and a camera.

 

Science investigations:

ECLIPSE is designed to meet four key science objectives for a nominal mission duration of four months (an extended mission will however be considered, with focus on network science):

(1) Determine the interior structure of the Moon to better understand the formation and evolution of the Earth-Moon System. ECLIPSE will greatly advance our understanding of the Moon’s deep interior by using a single seismic station to measure S-P differential travel times from Deep Moonquakes, as well as secondary seismic phases. These data will improve tomographic models, enhance precision in seismic attenuation analysis, and help investigate the presence of partial melt in the mantle. The mission may also detect seismic phases that traverse or reflect off the lunar core, offering new constraints on its size. Locally, high-sensitivity instruments will characterize crustal structure through receiver functions and noise autocorrelations. Electromagnetic data will enable magnetic sounding to infer mantle electrical conductivity structure. By combining seismic and magnetic field data, ECLIPSE will refine models of the Moon's crust and mantle mineralogy, state and temperature.

(2) Understand the current lunar bombardment rate. ECLIPSE will significantly improve estimates of the current meteoroid impact rate, a key factor for dating lunar and planetary surfaces. By combining ground-based [3] and space-borne (e.g., LUMIO) optical flash detections with ECLIPSE’s seismic recordings and uniquely identified seismic events, the mission significantly enhances impact detection capabilities. These observations will refine micrometeoroid flux estimates and improve constraints on impactor mass and velocity.

(3)  Monitor real-time environment affecting operation for potential future stable astrophysical and physics observatories. ECLIPSE will constrain the impact hazard using flux estimates from Objective 2 and monitor the vibrational environment for any possible future astronomical observatories, ensuring the safety of future human exploration. By constraining the fluctuations of the solar constant with the radiometer, correlations with the seismic noise and ground thermal contraction effects will be assessed, to better understand and mitigate the lunar seismic noise in the deci-hertz bandwidth, which is crucial for designing future gravitational wave detectors on the Moon.

(4)   Characterize the electrostatic environment at the surface of the Moon. Measuring DC electric fields on the Moon is key to understanding interactions between the regolith, plasma, and dust. Solar radiation and wind create strong surface potential differences, leading to complex charging phenomena. These fields, reaching hundreds of volts per meter, can lift dust and affect mission hardware. Accurate field measurements are essential for validating models and preparing for future lunar missions, including those requesting laser links potentially affected bv the levitated dusts.

 

Instrument suite:

The instrument suite is composed of eight instruments with TRL>= 7, inherited from past space missions (Table 1).

Instrument	Provider	Heritage
Very Broad Band seismometer (VBBZ)	IPGP, France	InSight Spare unit [1]; Same packaging as the lunar FSS [2]
Two geophones in horizontal configuration (GEOH)	ISAS, Japan	DragonFly-LunarA; Rebuilt sensor [4]
Geophone in vertical configuration (GEOZ)	ISAE-Supaero, France	Same as RAMSES mission
Electrical field sensor (Efly)	LATMOS, France	MicroARES; Rebuilt sensor [5]
Radiometer (RAD)	ROB, Brussels	PICARD; Rebuilt sensor [6]
Magnetometer (MAG)	IWF Graz, ÖAW, Austria, TUBS, Germany	BepiColombo, MMS, SOSMAG [7]
Camera (CAM)	Politecnico di Milano, Italia	Hera/Milani; RAMSES Cubesat
Acquisition electronics (Ebox)	ETH Zurich, Switzerland	InSight Spare Unit [8]

Table 1: Equipment list

Mission configuration:

Two mission configurations are currently under consideration. (1) The first option focuses on using high-TRL components, including a structure and thermal system originally developed by JPL for the FSS mission [2], combined with avionics derived from CubeSat technology. The primary constraint of this approach lies in the strict mass and volume limitations of the deployable unit, which unfortunately necessitates the removal of instruments which cannot use the common Ebox acquisition electronics (Magnetometer and Camera). The transportation to the Moon is proposed on the Argonaut lander. (2) The second option involves a European-led Surface Package, coordinated by an industrial partner. In this scenario, all instruments would be retained, and deployment would be managed by a European commercial Lunar Servicer, Argonaut, or by a US commercial Lunar Service. Given ongoing uncertainties about deployment costs, the ECLIPSE mission has been submitted to ESA under both the mini-F and F mission categories.

References:

[1] Lognonné et al., Space Sci. Rev., 10.1007/s11214-018-0574-6 (2019)

[2] Aboobaker et al., IEEE Aerospace Conference, 10.1109/AERO58975.2024.10521223 (2024)

[3] Sheward et al., Mon. Not. Roy. Astron. Soc., 10.1093/mnras/stad2707 (2024)

[4] Yamada et al., Planetary and Space Sci., 10.1016/j.pss.2008.12.004 (2009)

[5] Esposito et al., Space Sci. Rev., 10.1007/s11214-018-0535-0 (2018)

[6] Zhu et al., Geosci. Instrum. Method. Data Syst., 10.5194/gi-4-89-2015 (2015)

[7] Magnes et al., Space Sci. Rev., 10.1007/s11214-020-00742-2 (2020)

[8] Zweifel et al., BSSA, 10.1785/0120210071 (2021)