The LUSTER Mission Concept for Lunar-Based Asteroid and Comet Monitoring

Introduction: We present LUSTER (LUnar-based Survey for Time-domain Exploration and Research), a proposed NASA PRISM-SALSA lunar mission to study comets, asteroids, and exoplanet atmospheres using high-cadence, dual-band photometry from the Moon’s surface. This presentation focuses on LUSTER’s small body science objectives—specifically, its capability to characterize the evolving activity, surface properties, and dynamics of comets and Near-Earth Asteroids (NEAs). Featuring a compact 20-cm telescope deployed via NASA’s CLPS initiative, LUSTER will operate continuously for a full Lunar day (~14 Earth days), enabling uninterrupted near-ultraviolet (NUV) and visible (VIS) observations unconstrained by Earth occultation, diurnal cycles, or atmospheric interference (Fig. 1). It addresses a critical gap in small body research: the scarcity of high-cadence, synchronous NUV-visible data needed to unveil physical properties and track time-variable phenomena.

 

Figure 1. Dichroic transmission for LUSTER’s NUV and visible channels.

 

Science Goals - Comets: For comets, LUSTER’s dual-channel capability enables simultaneous imaging of gas and dust in cometary comae. The NUV channel is centered to the OH emission band near 315 nm, a direct tracer of water outgassing via photodissociation of H₂O, while the visible channel captures sunlight scattered by dust grains [1, 2] This configuration enables measurements of dust-to-gas ratio, which is a key diagnostic for understanding the physical and chemical drivers of cometary activity [3]. Additionally, morphological differences in the spatial distribution of gas and dust comae reveal the relative abundance, grain size distribution, and outflow dynamics of volatiles and refractories, which are shaped by nucleus properties and solar heating.  LUSTER will capture coma asymmetries, jets, and fragmenting structures in both bands, providing insight into the mechanisms governing mass loss, including sublimation, localized venting, and structural collapse. These signatures are expected to vary between short-period comets (which have undergone repeated solar processing) and long-period comets (which may retain more pristine volatiles), making LUSTER’s dual-band observations essential for comparative studies [4, 5]. Given a sustained multiple observation-per-day observing cadence, we will track temporal changes in dust and gas emission revealing both steady-state evolution and impulsive activity such as outbursts or fragmentation. LUSTER’s stable platform and uninterrupted viewing avoid the challenges of target visibility windows and Earth occultation that hinder space-based telescopes like HST. In preparation for this science, we are re-analyzing archival comet datasets (e.g., from HST and Swift) to benchmark gas and dust photometry across a variety of activity levels and heliocentric distances. We are also conducting simulated LUSTER observations using empirically motivated models of OH and dust brightness profiles. These simulations test our image extraction and analysis pipelines, particularly for tracking gas-to-dust ratios, assessing coma asymmetries, and detecting transient activity like fragmentation or rapid gas brightening.

 

Science Goals - NEAs: For Near-Earth Asteroids, LUSTER will generate high-cadence light curves in both NUV and visible bands, enabling the joint modeling of shape, rotation, and surface properties. By capturing light curves over multiple full rotations, LUSTER can resolve the shape and pole orientation of NEAs using light curve inversion techniques [6, 7]. These shape models are critical for refining non-gravitational forces such as the Yarkovsky effect, which depends sensitively on surface temperature distribution and rotation state. This, in turn, improves long-term orbit predictions and impact risk assessments [8]. LUSTER will observe both known and newly discovered NEAs with rapid rotation periods. The reflectance of asteroid surfaces in the NUV is highly sensitive to composition, texture, and degree of space weathering. This spectral range enhances contrast between silicate-rich and carbonaceous material and can identify subtle compositional heterogeneity that is undetectable in visible light alone [9]. Moreover, spectral differences between the NUV and visible light curves can reveal localized mineralogy or hydrated features, advancing our understanding of surface processes and enabling compositional classification at a level rarely achieved by small telescopes. Collectively, these observations will build a robust dataset of NUV-visible color indices, shape models, and light curves for a statistically meaningful sample of small bodies. These data will support both the scientific community and potential mission planning for planetary defense or resource utilization.

 

Target Selection: The initial small body target list includes >100 comets and asteroids brighter than V = 16 mag, observable at Earth elongations >30° within a potential 2028–2029 launch window. Given the annual discovery rate of >100 comets and >2,000 NEAs, this list is expected to expand significantly. A custom scheduling tool prioritizes exoplanet observations but efficiently interleaves the relatively short (20-minute) small body observations between them. In total, LUSTER will secure dozens of observations per object over the course of a single Lunar day as seen in Figure 2. 

 

Figure 2. LUSTER’s mock scheduler showing science operations: Exoplanets (39.4%), Comets (42.7%), and NEAs (11.2%).

 

Conclusion: The Moon provides an unmatched platform for time-domain UV-visible astronomy. Free from atmospheric absorption and weather variability, it allows full spectral access in the NUV and ~14 days of continuous viewing—far exceeding cadences achievable from Earth orbit. LUSTER combines high-cadence, dual-band imaging and a novel lunar vantage point to enable transformative Solar System science. By monitoring cometary activity and asteroid surface evolution over sustained timescales, it will advance our understanding of volatile transport, surface processes, and small body dynamics. Preparatory reanalysis of archival UV datasets, paired with realistic mission simulations, ensures readiness to extract maximum science from the data. As a pathfinder, LUSTER demonstrates the feasibility of lightweight, autonomous lunar telescopes and lays the groundwork for future networks of observatories that can continuously monitor the dynamic Solar System.

 

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