Deciphering the genesis and evolution of the Martian polar caps can provide crucial understanding of Mars' climate system and will be a big step forward for comparative climatology of the terrestrial planets. The growing scientific interest for the exploration of Mars at high latitudes, together with the need of minimizing the resources onboard landers and rovers, motivates the need for an adequate navigation support from orbit. In the context of the ARES4SC study, we propose a novel concept based on a constellation that can support autonomous navigation of different kind of users devoted to scientific investigations of those regions. We study two constellations, that differ mainly for the semi-major axis and the inclination of the orbits, composed of 5 small satellites (based on the SmallSats design being developed in Argotec), offering dedicated coverage of the Mars polar regions. We focus on the architecture of the inter-satellite links (ISL), the key elements providing both ephemerides and time synchronization for the broadcasting of the navigation message. Our concept is based on suitably configured coherent links, able to suppress the adverse effects of on-board clock instabilities and to provide excellent range-rate accuracies between the constellation's nodes. The data quality allows attaining good positioning performance for both constellations with a largely autonomous system. Indeed, we show that ground support can be heavily reduced by employing an ISL communication architecture. Periodic synchronization of the clocks on-board the constellation nodes with terrestrial time (TT) is enabled through the main spacecraft (the mother-craft), the only element of the constellation enabling radio communication with the Earth. We report on the results of numerical simulations in different operational scenarios and show that a very high-quality orbit reconstruction can be obtained for the constellation nodes using a batch-sequential filter or a batch filter with overlapping arcs, that could be implemented on board the mother-craft, thus enabling a high level of navigation autonomy. The assessment of the achievable positioning accuracy with this concept is fundamental to evaluate the feasibility of a future positioning system providing a global coverage of the red planet.

破译火星极冠的起源和演化可以提供对火星气候系统的重要理解，并且将是类地行星比较气候学向前迈出的一大步。科学界对高纬度火星探索的兴趣日益浓厚，同时需要最大限度地减少着陆器和漫游车上的资源，这促使人们需要轨道提供足够的导航支持。在 ARES4SC 研究的背景下，我们提出了一个基于星座的新概念，该星座可以支持致力于这些地区科学研究的不同类型用户的自主导航。我们研究了两个星座，主要在半长轴和轨道倾角上有所不同，由 5 颗小卫星组成（基于 Argotec 正在开发的 SmallSats 设计），提供火星极地地区的专门报道。我们专注于卫星间链路 (ISL) 的架构，这是为导航消息的广播提供星历表和时间同步的关键元素。我们的概念基于适当配置的相干链路，能够抑制机载时钟不稳定性的不利影响，并在星座节点之间提供出色的距离速率精度。数据质量允许为具有很大程度上自治系统的两个星座获得良好的定位性能。事实上，我们表明通过采用 ISL 通信架构可以大大减少地面支持。星座节点上的时钟与地面时间 (TT) 的周期性同步通过主航天器（mother-craft )，星座中唯一能够与地球进行无线电通信的元素。我们报告了不同操作场景下的数值模拟结果，并表明使用批处理顺序滤波器或具有重叠弧的批处理滤波器可以为星座节点获得非常高质量的轨道重建，这可以在船上实现mother-craft，从而实现高度的导航自主性。用这个概念评估可实现的定位精度对于评估未来提供红色星球全球覆盖的定位系统的可行性至关重要。