我国未来在轨监测火星沙尘暴的设想和方案

The orbit schemes to monitor Martian dust storms:Benefits to China’s future Mars missions

火星是地球的近邻,它的自转周期(约为24.6 h)及自转倾角(约为25°)都与地球的接近.火星公转周期为687 d,有稀薄的大气(主要成分为CO_(2)),有四季交替的气候变化,表面温度(夏天)最高时可达20°C.火星两极被冰(干冰和水冰的混合物)所覆盖,并有着消融和冰冻的季节周期变化.火星表面布满河道、峡谷、沟壑、冲积平原等地貌特征.在太阳系行星系统中,火星的气候环境最为接近地球.

Mars is most often the focus of planetary explorations because it promises to have signs of extraterrestrial life.China’s first Mars mission,called Tianwen-1,was launched on 22 May 2021 and was successful in“orbiting,landing and roving”the planet and exploring its environment.Following this success,China planned to carry out another Mars mission,known as Tianwen-3,to collect and return samples.However,dust storms posed a significant threat.Such activity on Mars has an evident pattern of seasonal variation,frequently occurring during spring and summer in the southern hemisphere.Under certain conditions,this dust activity can develop into a global storm,lasting several months,and can strongly perturb the upper atmosphere,which is crucial for the aerocapture of probes.Even regional storms can modify local visibility,temperature,wind,and the density of the lower and middle atmosphere,which impact parachutes,navigational imaging,and other decent-entry-landing and take-off probe processes.Indeed,the tiniest grains of dust pose a threat to human soft tissues and are harmful to the surface probes’mechanisms and filters.Solar panels,cameras,etc.,are also adversely impacted by dust deposition,which peaks during the fallout of a global dust storm.Thus,forecasting dust storms is invaluable for reducing or avoiding damage to these probes.However,the physical complexity of dust storms on Mars is not fully understood,making accurate forecasts of dust storms,and particularly their onset,challenging.To aid future Mars missions such as the Tianwen-3,we propose that China establish a network to monitor Martian dust storms and atmospheric weather that is based on observations of Mars from a spacecraft constellation.This constellation consists of three spacecraft in an equatorial synchronous orbit with an altitude of about 17000 km and one spacecraft in a large-elliptic polar orbit whose perigee altitude is about 150 km.The constellation with“four-point integration”can form a monitoring and alert network that provides simultaneous,continuous,and global-scale observations of the Martian atmosphere and surface.As an innovative platform for space-based science,this network has many advantages for Mars exploration,because it can monitor Martian dust storms and geomorphic changes on the surface,as well as the space environment and atmospheric weather.It is also beneficial for spacecraft relaying communication from probes on the Martian surface,allowing continuous data to be uplinked.Finally,the constellation is an ideal platform for on-orbit computing,delivering computer resources to surface assets,and global navigation of Mars.