250-m resolution lunar gravitational maps from gravity observed by satellites and gravity modelled from topography and 3D crustal density

Accurate knowledge of the lunar gravitational field is essential for lunar exploration, for instance, for gravity predictions at prospective landing sites, for inertial navigation or to establish a physically meaningful height system. This contribution presents a new suite of Lunar Gravitational Maps 2026 (LGM2026). LGM2026 is sampled at the resolution of 128 pixels per degree (~250 m at the equator) and surpasses LGM2011, the most detailed lunar surface gravitational model to date, by a factor of ~6. The 250-m resolution was reached by combining long-wavelength gravity observed by the GRAIL satellites (scales up to 11 km at the equator) with short-scale gravity inferred from LRO and Kaguya topography (scales from 11 km to 250 m). To make the modelling of short-scale signals realistic, LGM2026 relies on a 3D crustal density model as opposed to the constant-density assumption of LGM2011. LGM2026 depicts (i) the gravitational potential (useful for studying gravity-driven mass movements or flow direction of fluids), (ii) the full gravitational vector (gravity predictions at landing sites, inertial navigation, verification of accelerometer readings) and (iii) the full gravitational tensor (upward/downward continuation of the potential and vector data, spacecraft navigation). The maps shows the gravitational field at the lunar surface and on a sphere of the radius 1749 km passing outside of all masses. As a by-product, LGM2026 was converted into a series of external spherical harmonics up to degree 11,519. The purpose of LGM2026 is to provide a high-resolution gravitational model for applications that are sensitive to the variations of the lunar gravitational field such as gravity predictions at landing sites or inertial navigation. Given that the short-scale signals are derived from the topography instead of gravity observations, LGM2026 must not be geophysically or geologically interpreted at scales smaller than 11 km. The accuracy of LGM2026 is estimated to 2 mGal in terms of the gravitational vector. All LGM2026 maps use the principal axes coordinate system. The release of LGM2026 is scheduled to mid-2026. This work was funded by the EU NextGenerationEU through the Recovery and Resilience Plan for Slovakia under the project No. 09I03-03-V04-00273.