Photometric analysis of the Luna spacecraft landing sites

摘要

We investigate the influence of the rocket engine jets on the photometric properties of the landing sites of the Soviet sample return missions Luna 16, Luna 20, Luna 23, and Luna 24 using Lunar Reconnaissance Orbiter (LRO) Narrow-Angle Cameras (NACs) data, for which the geometric and photometric topography effects were corrected at the initial spatial resolution of the input data. Correlations between phase ratios and albedo for the landing areas are analyzed in order to assess the shape and spatial extent of the surface that was disturbed by the jet streams. We study the phase-angle dependences of the equigonal albedo for disturbed and undisturbed areas and find systematic differences related to regolith-structure changes. These disturbances could be destruction of the fairy-castle microstructure, removal of the thin upper layer of mature regolith, and smoothing the surface microroughness with a deposition from the dust clouds raised by the spacecraft exhausts of the landing and returning modules. We confirm that the position of the Luna 23 and Luna 24 landing sites were confused with each other.