A particle charge spectrometer for determining the charge and size of individual dust grains on Mars

摘要

Airborne dust is a primary factor influencing climate on Mars. Electrostatic charge carried by dust particles can play a role in their suspension, settling, and adhesion to spacecraft surfaces. Furthermore, the possibility for atmospheric discharges on Mars and the likelihood of associated hazards to robotic exploration remains an open and important question. In order to understand these aspects of the Martian surface environment, NASA is developing a portable instrument capable of measuring the charge and size of airborne particles. In the Particle Charge Spectrometer (PCS) the measurement of charge is based on direct capacitive coupling to a charge sensitive pre-amplifier. Aerodynamic particle diameter in the range from 2 to 100 micrometers is determined from the particle velocity in the sample inlet tube. Currently the field-portable device can measure charge on single particles with an error of less than 180 electronic charges and at a rate of over 200 particles per second. The goal of the research is to provide this measurement capability in an instrument that weighs under a kilogram and will operate in the Martian atmosphere with just a few watts of power. This paper describes the instrument and preliminary data from laboratory and field tests. The measurement approach is presented in the context of earlier particle charge instruments.