ESA's LUMIO Mission: detecting meteoroid impacts on the lunar farside

The Lunar Meteoroid Impact Observer (LUMIO) is a CubeSat mission designed to study meteoroid impacts on the Moon [1]. Developed under the European Space Agency’s General Support Technology Programme, LUMIO is a 12U CubeSat that will operate from a halo orbit around the Earth-Moon L2 point [2], providing continuous observations of the lunar farside. LUMIO is led by Politecnico di Milano and supported by the Italian Space Agency (ASI), the Norwegian Space Agency (NOSA), United Kingdom Space Agency (UKSA), and Swedish National Space Agency (SNSA). LUMIO has successfully passed Phases A and B and is currently set for Phase C, with launch foreseen in 2028.

By detecting Lunar Impact Flashes (LIFs), the brief bursts of light produced when meteoroids strike the Moon’s surface, LUMIO will extend the coverage of impact monitoring beyond Earth-based telescopes, which are limited to the nearside and affected by weather conditions [3]. The Moon, lacking an atmosphere, is constantly bombarded by meteoroids, ranging from millimeter-sized grains (hourly) to meter-scale objects (monthly). These impacts shape the lunar surface and pose a potential risk for future human and robotic assets that will inhabit the Moon for significant periods of time. A better understanding of the meteoroid population in the cislunar environment is required for future exploration of the Moon. Moreover, refining current meteoroid models is of paramount importance for many applications, including planetary science investigations. For instance, since meteoroids may travel dispersed along the orbit of their parent body, understanding meteoroids and associated phenomena can be valuable for the study of asteroids and comets themselves, and their dynamical paths. Studying meteoroid impacts can help deepening the understanding of the spatial distribution of near-Earth objects in the Solar System. The study of dust particles is also relevant to the topic of space weather. The ability to predict impacts is therefore critical to many applications, both related to engineering aspects of space exploration, and to more scientific investigations regarding evolutional processes in the Solar System.

Despite extensive ground-based monitoring, the impact flux on the Moon remains poorly constrained, particularly the latitudinal distribution and the millimeter to decimeter impactor size range [4]. LUMIO aims to address this gap by providing continuous, 

high-sensitivity observations, contributing to a more accurate characterization of the meteoroid population in cislunar space.

The mission’s primary instrument, LUMIO-Cam, is an optical sensor capable of detecting meteoroid impact flashes in both the visible and near-infrared spectral range (450-950 nm). This will allow LUMIO to quantify the frequency, location, and energy of impact events, improving models of impactor flux [5]. The LUMIO-Cam will provide continuous and full-disk coverage of the Moon’s farside, during the nominal duration of the scientific operations (one year). Synergies with other lunar-based missions such as NASA’s Lunar Reconnaissance Orbiter [6], will allow linking observed impact flashes with newly formed craters, and refining models of hypervelocity impact processes.

In addition to its primary science mission, LUMIO will conduct key technology demonstration experiments, such as an Autonomous optical navigation experiment.  LUMIO will test an optical autonomous navigation system that uses vision-based techniques to determine its position relative to the Moon [7]. The system relies on a limb-based navigation algorithm, processing images of the Moon’s illuminated limb to estimate the spacecraft’s location with sub-pixel accuracy. This experiment aims to reduce dependence on Earth-based tracking, demonstrating the feasibility of autonomous deep-space navigation for small satellites. The results will support future CubeSat missions requiring precise orbit determination without continuous ground station intervention.

According to the current timeline, LUMIO will be uniquely positioned to observe the asteroid Apophis during its near-Earth flyby in 2029. This event will present a rare opportunity to study the interaction of a potentially hazardous object with the Earth-Moon system. LUMIO’s instrument will be capable of observing Apophis for nearly one month before its close encounter and 2-3 days after it [8].

The scientific exploitation of LUMIO data is managed by the LUMIO Science Team, consisting of 62 members organized into six specialized working groups: (1) Meteoroid Characterization, (2) Surface Characterization, (3) Observation, (4) Impact Modelling, (5) Lunar Environment and Engineering, and (6) Citizen Science. Each group focuses on distdistinct research objectives aligned with the mission scientific goals.

Figure caption: Overview of the LUMIO mission. Top left: Moon phases and main direction of incoming meteoroids in the Earth-Moon system. Center and top right: LUMIO mission phases. Bottom left: LUMIO quasi-halo orbit around Earth-Moon L2 (lateral view). Bottom right: expected apparent size of the Moon as seen from LUMIO.

References: [1] Topputo F. et al. (2023) Icarus, 389, 115213. [2] Cipriano A. M. et al. (2018) Front. Astron. Space Sci., 5, 29. [3] Liakos A. et al. (2024) Astron. Astrophys., 687, A14. [4] Suggs R. M. et al. (2014) Icarus, 238, 23–36. [5] Merisio G. and Topputo F. (2023) Icarus, 389, 115180. [6] Robinson M. S. et al. (2010) Space Sci. Rev., 150, 81–124. [7] Panicucci P. et al. (2024) 46th AAS Guid. Nav. Control Conf., 1–20. [8] Gomiero et al. (in preparation).

Acknowledgment: LUMIO scientific activities are supported by Agenzia Spaziale Italiana (ASI-PoliMi agreement n. 2024-6-HH.0).