System design of a deep space microsatellite platform for Mars communication and navigation constellation

The Mars Communication and Navigation (MCN) mission is a multi-satellite constellation mission comprising 24 small satellites that shall prototype key technologies and provide an Earth-Mars communication and navigation infrastructure to enable a broad range of future exploration missions at Mars without the burden of having an expensive Earth link. The mission shall serve as a pioneer Comms/Nav network at Mars. The critical challenge lies in communicating with multiple users and relaying a high volume of data, in the order of few GB per day, and providing accurate positioning in the order of few metres for users simultaneously for 15 years. This work focuses on the systems design of the deep-space small satellite platforms used for MCN to satisfy the mission and performance objectives. The paper delineates the mission characteristics pertaining to the transport and deployment of the small satellites in a Walker-type constellation at Mars. System level requirements are defined and the principal design characteristics of the system, the key design constraints, and rationale behind the design choices are expounded. To address the challenge of communication, the system utilises K-Band and S-Band antennas for Forward/Return link with orbiters, autonomous rovers, landers/ascenders, and human landing missions at Mars. A Ka-Band deployable dish antenna is utilised to relay the user data via a larger Gateway/Relay satellite located in Sun-Mars L1 to the Earth Ground Stations. A multi-channel deep-space transponder is utilised for near-real time data relay and navigation service. To provide GNSS-like service at Mars, the system houses an on-board atomic clock (RAFS) for providing high accuracy positioning. In addition, a Mars Ground Segment is required to guarantee the accuracy of the navigation service. The system utilises equipment that are Commercial Off-The-Shelf (COTS), some with modifications, to obtain a cost-effective solution. A novel design concept is used for solar arrays and the electrical power system to satisfy the large power needs. The system also utilises an in-house on-board processing and data handling system as well as in-house power control and distribution unit. The key technologies that require further development are also highlighted. Finally, system budgets are obtained to show design feasibility and the structural composition of the MCN small satellite platform is detailed. The overall mass of the platform is 60 kg with a 27U+ form factor. The MCN project is funded under ESA Contract No.4000131323/20/NL/MG.