Abstract Earth observation is one of the most important satellites’ applications. Past earth observation systems have used traditional space technology to achieve the best possible performance, but have been very expensive. Recently, thanks to advancements in technology and modern microelectronics, small satellites have become more and more useful at much lower costs, even if with reduced performance. The resolution of the optical payload improves as the altitude is reduced. Space system mass is proportional to the cube of the linear dimensions. This means that by flying at lower altitudes, satellites can reduce their payload size and therefore the entire mass of the satellite, thus reducing the cost of the system dramatically. However, almost all the earth observation missions fly at the minimum altitude that provides a sufficient orbital life. The addition of a propulsion system capable of providing drag compensation for the entire satellite operative life provides the possibility to fly at very low earth orbit. In this way, the same performance can be obtained with a smaller and cheaper system. To obtain the same coverage more units are needed to replace a larger unit at higher altitude. In this paper it is confirmed that future smallsat observation systems, operating at a lower altitude than traditional systems, have the potential for comparable or better performance, much lower overall mission cost (by a significant factor), lower risk (both implementation and operations), shorter schedules, lower up-front development cost, more sustainable business model, to be more flexible and resilient, more responsive to both new technologies and changing needs, and to mitigate the problem of orbital debris. This paper focus in particular on the effect of the propulsion system parameters (performance and costs) on the cost model as a function of the altitude. It is demonstrated that new affordable chemical propulsion systems provide already significant benefits with limited constraints, allowing a useful reduction of altitude and, consequently, costs. Electric propulsion systems have the potential to allow even lower altitudes or longer lifetimes; however, they have a stronger impact on the satellite design related to their power consumption, generally requiring deployable solar panels, which can limit the flexibility in the orbit selection or the added weight and cost of batteries. The development of electric thrusters that have good performance and limited impact on the satellite architecture (particularly at small scales) is fundamental to exploit their potential for reduced mission costs through very low altitude flight.

中文翻译：

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推进系统特性对极低高度地球观测任务成本降低潜力的影响

摘要 对地观测是卫星最重要的应用之一。过去的地球观测系统使用传统的空间技术来实现最佳性能，但成本非常高。最近，由于技术和现代微电子技术的进步，即使性能有所下降，小型卫星也变得越来越有用，而且成本要低得多。光学有效载荷的分辨率随着高度的降低而提高。空间系统质量与线性维度的立方成正比。这意味着通过在较低的高度飞行，卫星可以减少其有效载荷大小，从而减少卫星的整体质量，从而显着降低系统成本。然而，几乎所有的地球观测任务都在提供足够轨道寿命的最低高度上飞行。能够为整个卫星工作寿命提供阻力补偿的推进系统的添加提供了在极低地球轨道上飞行的可能性。这样，可以用更小更便宜的系统获得相同的性能。为了获得相同的覆盖范围，需要更多的单位来替换更高海拔的更大的单位。在本文中，证实未来小卫星观测系统在比传统系统更低的高度运行，具有可比或更好的性能、更低的总体任务成本（一个重要因素）、更低的风险（实施和操作） ，更短的时间表，更低的前期开发成本，更可持续的商业模式，更加灵活和有弹性，对新技术和不断变化的需求更加敏感，并减轻轨道碎片问题。本文特别关注作为高度函数的推进系统参数（性能和成本）对成本模型的影响。事实证明，新的负担得起的化学推进系统已经在有限的限制下提供了显着的好处，可以有效地降低高度，从而降低成本。电力推进系统有可能实现更低的高度或更长的使用寿命；然而，它们对与功耗相关的卫星设计有更大的影响，通常需要可部署的太阳能电池板，这可能会限制轨道选择的灵活性或电池的额外重量和成本。