Dynamic Model of the Dust Cloud Around the Moon

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The data gathered by the LDEX detector onboard NASA’s LADEE mission shows that there is a permanent, asymmetric dust cloud around the Moon. The density of the dust grains in the cloud varies with annual meteoroid showers. Micron sized secondary ejecta particles generated by these meteoroid showers and interplanetary dust are considered as the main source of the lunar dust cloud. Our ultimate goal is the development of a dynamic model for the lunar dust cloud, and in this project we will focus on the main input of this model: distributions of micron sized ejecta grains with high speeds. For this, micron sized particles will be accelerated by the electrostatic dust accelerator located at IRS, the University of Stuttgart, and millimeter sized particles will be fired by a light gas gun operated by the Chinese partner, the Harbin Institute of Technology (HIT).The accelerated projectiles will cover the size range of 0.1 µm - 10 mm with speeds varying from 500 m/s to 50 km/s, to simulate the properties of meteoroid shower particles and interplanetary dust particles impacting on the lunar surface. The incident angles will vary from 15° to 90°. A PVDF detector array and an aerogel collector array will be designed to be able to monitor the mass, speed and angular distributions of ejecta grains created by the millimeter sized projectiles. The ejecta generation due to micron sized projectiles can be investigated with a multi-anode detector system and a delay line detector system. The target will be CSA-1 lunar regolith simulant, which was developed by the Chinese partner. The primary impactor flux onto the surface of the moon is determined using the latest models describing the meteoroid environment at the moon. These models are called IMEX and IMEM2 and were developed by the german partner. The models provide the flux, mass, velocity and angular distributions of the impacting grains. The experiments performed in this project characterize the secondary ejecta generated by the impacts. The ejecta dynamics is then modelled in order to fit the LDEX observations of the lunar dust cloud.Both parties have a lot of experience on space environments and hypervelocity impact research. All experimental tests and simulation studies are planned to be carried out using in-house acceleration facilities operated by the parties after 2019 allowing them to plan and perform the measurement campaigns in a time and cost efficient manner. The two parties have a long history in cooperation due to an early exchange of personnel (Dr. Li). Dr. Ing Ralf Srama is a foreign expert working at HIT with funds from the Chinese ‘111 Plan’ project, and he is the project leader of the development of a 3.5 MV dust accelerator located at HIT. The new development of a space environment model will allow German and Chinese space scientists to be in a world-wide leading position to explore new areas of astronomy and planetary science.