An Expanded Deep Space Relay Architecture for Improved Communication and Navigation

In our previous paper, a baseline relay architecture was developed to provide optical communication with Mars and trilateration-based navigation services to deep space users. The baseline architecture used Mars-leading and trailing orbits to ensure continuous optical communication with Mars during conjunction, while also providing suitable geometric diversity for trilateration. This paper addresses the design, performance, and feasibility of two expansions to the baseline architecture: a third relay in a Sun-Mars L2 Halo orbit, and opportunistic reconfiguration of the lead and trail relays.Communication and navigation tradeoffs inform the design of the expanded architecture. The design parameters considered include the shape and size of the halo relay orbit and the separation angles of the lead/trail relays. The communication benefits of the expanded architecture are analyzed on the bases of additional access time and additional downlink capacity for Mars users. Navigation performance is evaluated based on a dilution of precision (DOP) analysis, which quantifies the geometric quality of the architecture for trilateration and a covariance analysis, which maps expected levels of range measurement error to position estimate error. The feasibility of the expanded architecture is assessed based on the propulsion requirements needed to deliver suitably sized telecom payloads to the desired relay orbits. Both impulsive and non-impulsive methods are considered.The addition of a halo relay to the architecture was found to benefit communication performance by providing more access opportunities and higher downlink bandwidth than the baseline throughout the synodic period. The halo relay also benefitted navigation by enabling trilateration via a one-way ranging scheme, or a two-way ranging scheme that could operate independent of the DSN. Reconfiguration of the lead and trail relays relative to Mars was found to improve data rates compared to the baseline architecture, but at the expense of navigation quality. Insertion of the lead, trail, and halo relays into their respective orbits was found to be achievable with reasonable propulsive abilities.