Optical response of a single non-spherical particle and a correction scheme for the dust detection system onboard Tianwen-2

The dust detection system (DDS), a subsystem of the dust multi-properties analyzer (DMA) onboard the Tianwen-2 mission, was designed for in situ measurement of the sizes and velocities of dust particles near asteroid 311P/PanSTARRS using the laser-scattering techniques. Ground calibrations with spherical particles enable the establishment of a polynomial retrieval function, which results in a satisfactory accuracy in size detection [ Appl. Opt. 64 , 4851 ( 2025 ) APOPAI 0003-6935 10.1364/AO.558537 ]. However, the irregular morphologies of natural dust particles introduce systematic deviations. As a companion piece of [ Appl. Opt. 64 , 4851 ( 2025 ). APOPAI 0003-6935 10.1364/AO.558537 ], this paper focuses on the analysis of the optical response of non-spherical dust analogs in the DDS, both experimentally and theoretically. Laboratory tests were conducted with apatite, anhydrite, and fluorite particles. Theoretical calculations of the scattered flux of particles, whose geometries were modeled as spheroids, are implemented using the T-matrix method to reveal the influence of elongation and orientation on scattering. By introducing elongation-dependent correction factors into the polynomial retrieval function, the size retrieval deviation for irregular anhydrite and apatite particles was reduced to below 18%. This work provides a practical correction strategy to enhance the reliability of in situ size measurements during Tianwen-2’s rendezvous with 311P/PanSTARRS.