Cislunar Navigation

Cislunar Navigation refers to positioning and trajectory determination in the region of space between Earth and the Moon, encompassing lunar transfer orbits, lunar orbit insertion, Earth-Moon Lagrange point halo orbits (L1, L2, L4, L5), and Near-Rectilinear Halo Orbits (NRHO) - the planned orbit of NASA's Lunar Gateway station.

Cislunar space presents unique navigation challenges that distinguish it from both near-Earth and deep space operations. GPS signals are available but extremely weak and geometrically unfavorable (all satellites below the spacecraft). Traditional ground-based tracking requires dedicated lunar relay satellites or direct DSN contacts, which are limited in availability. The gravitational dynamics are complex, governed by the three-body problem (Earth-Moon-Sun), making orbit prediction and maintenance computationally demanding.

Kepler Nav's cislunar navigation capability leverages the Lie Group manifold filter's coordinate-system invariance - the filter operates in the same mathematical framework regardless of whether the primary gravitational body is Earth, the Moon, or a combination. The observability matrix maintains full rank (6/6) at all five Earth-Moon Lagrange points, verified through analytical Lie derivative computation and numerical simulation across thousands of orbital geometries.

For lunar surface operations, the system transitions to a terrain-relative navigation mode using optical landmark tracking combined with gravitational gradient sensing, providing autonomous positioning on the lunar surface without any deployed navigation infrastructure.