Astronomical Optical Interferometry from the Lunar Surface

TL;DR

This study evaluates the scientific payoff and technical feasibility of deploying astronomical optical interferometry on the lunar surface. It integrates mature Earth-based interferometry with rapidly advancing lunar access (CLPS, Artemis) to outline architectures, environments, and mission concepts across small, Explorer, and flagship scales. Key contributions include a detailed assessment of lunar advantages (coherence, sky access), environmental challenges (dust, seismic, thermal), and practical mitigation strategies; plus strawman concepts and program pathways that align with NASA astrophysics, planetary science, and international collaborations. The work argues that phased lunar interferometry can achieve sub-milliarcsecond imaging and micro-arcsecond astrometry, enabling transformative science from brown dwarfs and YSOs to exoplanet masses and AGN structure, while leveraging a burgeoning lunar economy to enable sustained operations.

Abstract

The lunar surface is a compelling location for large, distributed optical facilities, with significant advantages over orbital facilities for high spatial resolution astrophysics. The serious development of mission concepts is timely because of the confluence of multiple compelling factors. Lunar access technology is maturing rapidly, in the form of both US-based crewed and uncrewed landers, as well as international efforts. Associated with this has been a definitive maturation of astronomical optical interferometry technologies at Earth-based facilities over the past three decades, enabling exquisitely sharp views on the universe previously unattainable, though limited at present by the Earth's atmosphere. Importantly, the increasing knowledge and experience base about lunar surface operations indicates it is not just suitable, but highly attractive for lunar telescope arrays.

Figures (31)

• Figure 1: Motivations for the Keck Institute for Space Studies Study Program: rapid advances in lunar surface access (left) with missions such as those from NASA CLPS, along with multiple decades of demonstrated operations of terrestrial optical interferometry, such as the Palomar Testbed Interferometer (right).
• Figure 2: Radio VLBI observations of the inner regions of the radio jets in 3C 84 Nagai2014, BL Lacerta Gomez2016, and the binary AGN candidate 0402+379 Rodriguez2006 (left to right). The 3C 84 and BL Lac jet structures, and the binary separation, are at milliarcsecond angular scales corresponding to $\sim$parsec linear scales. The target brightnesses ($m_V \sim 12.5-17$) put them out of reach of terrestrial optical interferometry.
• Figure 3: Much of the expected interior structure of AGNs is inferred from much larger-scale imaging (Figure \ref{['fig:agn_examples']}); optical interferometry will be able to directly image these structures Cackett2021iSci...24j2557CGutierrez2024arXiv240514843G.
• Figure 4: The angular resolution challenge of young stellar objects (YSOs).
• Figure 5: Difference between brown dwarf radii estimated with evolutionary and atmospheric models as a function of spectral type. Significant discrepancies exist at the M-to-L type transition boundary Sanghi2023ApJ...959...63S.