Geometric properties of water-ice clouds as observed from Jezero Crater in the first 600 sols with the NavCam Instrument onboard Mars2020 Rover, Perseverance

In the first 600 sols of the Mars2020 mission, LS 5.6o to 316.8o, 46 cloud movies and 145 cloud surveys were collected to observe clouds at Jezero Crater, the landing site of Perseverance Rover. Cloud movies were processed using the Mean Frame Subtraction (MFS) method revealing cloud structures, which were subsequently analysed using digital image processing. Two-dimensional Fast Fourier Transforms (FFT) were used to compute cloud structure sizes ranging from 2.90 km to 15.25 km for clouds between 30 km to 50 km altitude, based on coincident Mars Climate Sounder (MCS) vertical profiles of atmospheric water-ice. Same-value thresholding was utilized to detect the cloud structures in MFS-processed and projected cloud movies. The resolution dependence needed to resolve these structures over various thresholds was examined to find multifractal scaling of Mars clouds for resolutions between 0.1 km and 1.6 km. We characterize the multi-scaling observed in the images and its implications for the design of cloud-tracking cameras from the surface as well as cloud-resolving models.

在火星2020任务的前600个火星日（sol）期间，太阳经度（L_s）从5.6°到316.8°，研究人员在毅力号火星车（Perseverance Rover）着陆点杰泽罗陨石坑（Jezero Crater）收集了46段云影片和145次云调查数据，用于观测云层。云影片采用均值帧减法（Mean Frame Subtraction, MFS）处理以揭示云结构，随后通过数字图像处理对这些结构进行分析。基于同步获取的火星气候探测仪（Mars Climate Sounder, MCS）大气水冰垂直剖面数据，研究人员使用二维快速傅里叶变换（Two-dimensional Fast Fourier Transform, FFT）计算了高度在30 km至50 km之间云层的结构尺寸，其范围为2.90 km至15.25 km。在经MFS处理和投影的云影片中，采用等值阈值法（Same-value thresholding）检测云结构。研究人员考察了在不同阈值下解析这些结构所需的分辨率依赖性，以确定分辨率在0.1 km至1.6 km范围内火星云层的多重分形标度特性。我们描述了图像中观测到的多尺度特性，及其对地表云跟踪相机设计和云解析模型构建的启示。