Exploration of Mars and establishment of human settlement have been of sharp interest for several decades. Since the turn of the century, efforts have been ramped up to make these a reality. With the execution of multiple robotic exploration missions and several more planned missions in the next two decades, as well as serious plans for human landing missions, a key need is the establishment of accurate, reliable, expansive, and cost-effective positioning and communication service for several users in the Mars environment. The Mars Communication and Navigation (MCN) mission is a multi-satellite constellation at Mars that shall provide data relay and positioning services for the identified possible users, that are orbiters, landers, ascenders, autonomous rovers, and human landing missions. The aim of MCN is to investigate and prototype key technologies for a Mars positioning and communication system using small satellites, in order to enable the development and operations of a wide range of Mars missions, providing a backbone Earth–Mars communication and navigation infrastructure. This work focuses on the critical architectural aspects of the MCN. The end-to-end (E2E) system architecture is presented, in order to provide an overview of the space and ground segments along with the operations concepts. Concerning the orbital configuration, the constellation and its deployment strategy are discussed. The MCN constellation baseline comprises 24 microsatellites operating in a Walker-like orbital configuration at Mars to provide service for more than 70 users potentially. Moreover, a Relay/Gateway link is utilized to serve as a communication bridge between Earth ground segment and the MCN constellation. Concerning the communication and navigation aspects, their architectures and possible solutions are highlighted, together with an overview of the related critical technologies required to achieve the mission objectives
