Surface Properties and -Processes on Phobos from Spectrophotometric Data by HRSC (High Resolution Stereo Camera) on Mars Express

我们将描述火卫一的分光光度特性，以提高我们对火卫一表面结构的理解，以及在这颗火星卫星上观察到的不同反照率和颜色模式的动态过程。我们受益于火星快车上HRSC（高分辨率立体相机）最新的窄带彩色和全色数据，这些数据来自大范围的照明相位角和高空间分辨率。HRSC覆盖了火卫一的后半球和背面，这是目前其他绕火星轨道运行的航天器无法观测到的。从超过327次火卫一飞掠中获得的数据，预计还会有更多的数据。我们确定了圆盘分辨率的光度函数，该函数将用于绘制火卫一表面的光度特性，并识别局部反照率异常，例如地表粗糙度增加的区域。此外，我们利用来自HRSC颜色通道的数据在相机的高空间分辨率下绘制火卫一表面的多光谱特性。我们的测绘结果将与以前任务的仪器数据进行比较，在以前的任务中，火卫一著名的“红色”和“蓝色”光谱单元已经被确定。火卫一的风化层和多光谱单元的特征将从表面结构和动力学过程（如火山口喷出物的就位和空间风化）的角度进行讨论。我们提出的项目是及时的，因为MMX（火星月球探测器），JAXA的火卫一样本返回任务，目前正在准备中。我们将对着陆点的选择和采样策略提出建议，以最大限度地提高即将到来的任务的科学回报。来自柏林工业大学和DLR行星研究所的团队在开展这项拟议的研究方面经验丰富。

We will characterize the spectrophotometric properties of Phobos to improve our understanding of the surface structure and the dynamic processes causing the distinct albedo and color patterns observed on this Martian satellite. We benefit from most recent narrow-band color and panchromatic data by HRSC (High-Resolution Stereo Camera) on Mars Express, obtained from a wide range of illumination phase angles and at high spatial resolution. The HRSC coverage includes Phobos’ trailing hemisphere and the farside, not observable by other currently Mars-orbiting spacecraft. Data from more than 327 Phobos flybys are available, and more data are expected to come. We determine disk-resolved photometric function(s), which will be used to map photometric properties of Phobos’ surface and to identify local albedo anomalies, representing e.g., areas of increased surface roughness. Furthermore, we use data from HRSC color channels to map multispectral properties of Phobos’ surface at the camera’s high spatial resolution. Results of our mapping will be compared with instrument data from previous missions, where Phobos’ well-known „red“ and „blue“ spectral units have been identified. The characteristics of Phobos’ regolith and the multispectral units will be discussed in terms of surface structure and dynamic processes, such as emplacement of crater ejecta and space weathering. Our proposed project is timely in the light of MMX (Martian Moon Explorer), JAXA’s sample return mission to Phobos, which is currently being prepared. We will make recommendations for choices of landing sites and sampling strategy to maximize the science return of this upcoming mission. The team from Technical University Berlin and the DLR Institute of Planetary Research is uniquely experienced to carry out this proposed study.