Exploring the Clouds of Venus: Science Driven Aerobot Missions to our Sister Planet

Venus is essential to our understanding of the evolution and habitability of Earth-size planets throughout the galaxy. The selection of the VERITAS, EnVision, and DAVINCI missions by NASA and ESA in June 2021 is an important step in advancing the science. However, addressing many of the most challenging questions will require in situ platforms that can operate in the Venus environment for extended periods in order to capture the full complexity of our sister planet. Aerobots are aerial vehicles that exploit buoyancy to achieve long-duration operation in the Venus cloud layer where environmental conditions are comparatively benign. Buoyancy control, explained in more detail in a companion paper at this conference, allows aerobots to change altitude with little energy expenditure enabling new scientific measurement opportunities. These include atmospheric chemistry, dynamics, geophysical measurements of the crust and interior and geological investigations enabled by high resolution surface imaging. One aspect to our approach to defining missions that fit within the resource constraints of competitive missions is keeping the scale small. Today’s science-driven appetite for sophisticated measurements and large volumes of data is driving size upwards but advances in technology can enable aerobots that can be delivered to Venus at manageable costs. The other aspect is supporting the aerobot at Venus with orbiters providing data relay, localization and synergistic science. The recently selected orbiters, equipped with low-cost proximity relay systems routinely used at Mars may obviate the need for dedicated orbiters thereby enabling Discovery mission candidates. Four aerobot mission concepts have been defined which fit comfortably within the current New Frontiers (NF) cost cap ($900M in $FY22). One of these concepts would also be a candidate for a Discovery mission if that cost cap ($500M in $FY19) were raised. Raising the NF cost cap would enable more capable aerobot missions combining both altitude control with synergistic orbital observations. Investigations of surface geology at high resolution with subcloud NIR nightside imaging and dropsondes on the dayside of Venus could also benefit from collaborations with foreign contributions.

金星对于我们理解银河系内类地行星的演化与宜居性至关重要。2021年6月，美国国家航空航天局（National Aeronautics and Space Administration, NASA）与欧洲空间局（European Space Agency, ESA）选定VERITAS、EnVision及DAVINCI三项金星探测任务，这是推动该领域科学发展的重要里程碑。然而，要解答诸多极具挑战性的科学问题，我们需要能够在金星环境中长期运行的原位探测平台（in situ platform），以全面揭示这颗姊妹行星的完整复杂性。浮空探测器（aerobots）是利用浮力实现在金星云层中长时间运行的航空飞行器，该区域的环境条件相对温和。如本次会议附属论文中详述的浮力控制系统，可让浮空探测器以极低能耗实现高度调节，从而开辟全新的科学测量途径，涵盖大气化学、大气动力学研究，地壳与内部结构的地球物理探测，以及依托高分辨率地表成像开展的地质调查。我们在设计符合竞争性探测任务资源约束的任务方案时，核心思路之一是保持任务规模小巧：当前，科学研究对高精度测量与海量数据的需求正推动任务规模扩大，但技术进步已可实现以可控成本向金星部署浮空探测器。另一核心思路则是依托轨道器为金星浮空探测器提供数据中继、定位服务以及协同科学观测支持。近期选定的轨道器搭载了火星探测中常用的低成本近距中继系统，这或可免去专用轨道器的研发需求，从而使发现级任务（Discovery）候选方案成为可能。目前已定义四款浮空探测器任务方案，其成本均符合当前“新前沿”（New Frontiers, NF）任务的成本上限（2022财年FY22下为9亿美元）。若将发现级任务的成本上限（2019财年FY19下为5亿美元）提升，其中一款方案也可作为该级任务的候选项目。提升“新前沿”任务的成本上限，可支持兼具高度调节能力与协同轨道观测功能的更先进浮空探测器任务。借助金星夜间云下近红外（Near-Infrared, NIR）成像与昼间探空仪开展的高分辨率地表地质调查，也可通过国际合作获得助力。