Laboratory testing and data analysis of the Electrostatic Lunar Dust Analyzer (ELDA) instrument

We report the advance development of the Electrostatic Lunar Dust Analyzer (ELDA) instrument for the detection of individual low-velocity micron-size dust particles mobilized near the lunar surface, and the measurement of the dust charge, velocity vector, and mass. The first article ( N. Duncan et al., Planet. Space Sci., 2011 ) described the measurement principle, optimized instrument geometry, and the initial testing performed on air. The full laboratory prototype of ELDA has now been completed and tested under vacuum. The numerical data analysis is improved to include gravitation and the calculation of the particle's mass. The ELDA operation principle is based on sensing a charged dust particle by an array of wire electrodes as it is passing though the instrument. Each wire electrode is connected to a charge sensitive amplifier and the velocity vector is reconstructed from the signal shapes and amplitudes. Within the instrument, a strong electrostatic field is used to deflect the trajectories of the particles. The dust mass is determined from the change in velocity measured before and after deflection. The instrument is tested using particles with 54 μm mean radius and a narrow size distribution. The experimental results and the error analyses show that ELDA can measure the mass of individual particle with a factor of two even for very low signal to noise ratio.