Is it possible to integrate Electric Propulsion thrusters effectively on Very Low Earth Orbit Microsatellites?

本文描述了研究在超低地球轨道（<200公里）微型卫星（质量<125公斤）上有效使用电力推进的可行性的工作。目标是提供20-100公斤范围内的高性能卫星，适用于广泛的任务，可以在轨道上实现至少一年的使用寿命。在160公里的高空操作遥感卫星有很多好处。成像仪越接近目标，成像仪就越小，从而有可能使用纳米卫星（<30公斤），从而减小尺寸和成本。与500公里的卫星相比，极低地球轨道卫星可以实现焦距减少3倍，射频功率减少30倍，并显着提高下行数据速率。总的来说，这可能导致总成本降低10倍。由于在这些低空增加的空气密度，卫星会经历更大的阻力，这通常会导致它在几个月内脱离轨道。使用电力推进系统来对抗增加的阻力，可以延长使用寿命。欧洲航天局（ESA）的重力场和稳态海洋环流探测器（GOCE）证明了这一点，该探测器在燃料耗尽之前使用电力推进在260公里的轨道高度维持了55个月。如上所述，有兴趣使用小于200公里的轨道，比地球自转轨道低得多，其大气密度更高，因此阻力更大。因此，有必要对阻力和轨道进行建模，以便了解与轨道的其他扰动相比，空气密度在这个高度所起的作用更大。一旦阻力水平确定，就可以选择电力推进的类型。执行了推进类型到任务类型的映射，以帮助选择过程。纳米卫星的阻力建模是使用直接模拟蒙特卡罗技术实现的，然后将其与标准轨道建模技术相结合，以确定电力推进装置的尺寸。

This describes work to investigate the feasibility of using Electric Propulsion on Ultra Low Earth Orbit (<200km) Microsatellites (mass <125kg) effectively. The aim is to provide a highly capable satellite in the 20-100 kg range, applicable to a wide range of missions which could achieve a lifetime of at least one year in orbit.Operating a remote sensing satellite at 160km has many benefits. The closer the imager is to a target, the smaller this imager can be, leading to the possibility of using nanosatellites (<30kg) with consequent size and cost reductions. Compared to a satellite at 500 km, a Very Low Earth Orbit Satellite may achieve 3x reduction in focal length as well as up to 30x reduction in RF power with a significantly improved downlink data rate. Altogether this could lead to a 10x reduction in the overall cost.Due to increased air density at these low altitudes a satellite experiences larger drag forces which would normally cause it to de-orbit within a few months. An increased operational lifetime can be achieved using an electric propulsion system to combat the increased drag. This was demonstrated by the European Space Agency's (ESA) Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) which sustained an orbital altitude of 260km using electric propulsion for 55 months before running out of fuel.As described above, there is an interest in using orbits of less than 200km, considerably lower than GOCE, which have a higher atmospheric density and therefore higher drag. It was therefore necessary to model both the drag and orbit in order to understand the increased role that the air density played at this altitude in comparison to other perturbations of the orbit. Once the level of drag was established, the type of electric propulsion could be selected. A mapping of propulsion types to mission types was performed to aid this selection process. Modelling of the drag for the nanosatellite was achieved using direct simulation Monte Carlo techniques and this was then combined with standard orbit modelling techniques to size the electric propulsion unit.