Dynamic Model of the Dust Cloud Around the Moon

NASA LADEE任务上的LDEX探测器收集的数据显示，月球周围有一个永久性的、不对称的尘埃云。云中尘埃颗粒的密度随着每年的流星雨而变化。这些流星雨和星际尘埃产生的微米级次级抛射粒子被认为是月球尘埃云的主要来源。我们的最终目标是开发一个月球尘埃云的动力学模型，在这个项目中，我们将专注于该模型的主要输入：微米级高速抛射颗粒的分布。为此，位于斯图加特大学美国国家航空航天局的静电尘埃加速器将加速微米级粒子，并由中方合作伙伴哈尔滨工业大学(HIT)操作的轻气炮发射毫米级粒子。加速后的射弹将覆盖0.1微米-10毫米的范围，速度从500米/S到50公里/S，以模拟流星体簇射粒子和星际尘埃粒子撞击月球表面的性质。入射角将在15°到90°之间变化。将设计一个PVDF探测器阵列和一个气凝胶收集器阵列，以能够监测毫米尺寸弹丸产生的抛射颗粒的质量、速度和角度分布。用多阳极探测器系统和延迟线探测器系统可以研究微米级弹丸的抛射产生。目标将是由中国合作伙伴开发的CSA-1月壤模拟器。月球表面的主要撞击通量是使用描述月球流星体环境的最新模型确定的。这些型号被称为IMEX和IMEM2，由德国合作伙伴开发。这些模型提供了撞击颗粒的流量、质量、速度和角度分布。本项目中进行的实验表征了撞击产生的二次喷出物。然后建立抛射动力学模型，以符合LDEX对月球尘埃云的观测。双方在空间环境和超高速撞击研究方面都有丰富的经验。所有实验测试和模拟研究计划在2019年后使用缔约方运营的内部加速设施进行，使其能够以及时和具有成本效益的方式规划和开展测量活动。由于双方很早就进行了人员交流，双方的合作历史悠久(李博士)。Ralf Srama博士是HIT利用中国“111计划”项目资金工作的外国专家，他是HIT 3.5 MV尘埃加速器开发的项目负责人。空间环境模型的新发展将使德国和中国的空间科学家在探索天文学和行星科学的新领域方面处于世界领先地位。

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.