LDEX: Lunar Dust EXperiment

The lunar dust environment is expected to be dominated by submicron sized dust particles released from the Moon due to: a) the continuous bombardment by interplanetary dust, and b) due to plasma-induced, intense, small-scale electric fields. To a good approximation, the impact-produced ejecta are expected to form a spherically symmetric, continuously present cloud, while the electrically lofted population is expected to be concentrated over the terminators, and remain highly temporally and spatially variable. The Lunar Dust EXperiment (LDEX) instrument is proposed for the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission for in-situ dust detection in orbit around the Moon. LDEX is based on the detection of ions generated in hypervelocity dust impacts. The instrument is capable of detecting submicron sized dust grains with impact speeds above about 1 km/s. Particles larger than about 0.2 microns can be detected individually, and the parameters of the impact signal yield the mass, velocity, and charge of the dust. Smaller dust grains, below the detection threshold for individual detection, are measured collectively as an average from a large number of impacts. With the extended detection size range, LDEX can verify the existence of the putative lunar dust-exosphere. LDEX has been recently developed at LASP, and it has a high degree of heritage based on similar instruments on the Ulysses and Galileo missions. An engineering prototype version of LDEX is scheduled for testing and calibration at the Heidelberg dust accelerator facility. The talk will briefly review the science goals and measurement requirements for in situ dust detection, as well as the capabilities of LDEX.