A Comparison of Navigation Methods Enabled by a Deep Space Relay Architecture

A deep space relay architecture for communicationand navigation was developed in two previous papers. Thebaseline architecture, consisting of a Mars leading and a Marstrailing relay, was designed to mitigate the Mars conjunctionproblem for optical communication while enabling deep spacetrilateration for inner solar system users. An expanded versionof the architecture added a Mars halo relay which improved thearchitecture’s data throughput and navigation potential.This paper further defines the navigation component of thearchitecture. Previous analysis assumed trilateration withidealized, instantaneous one- and two-way range measurements.Here, four realistic methods for deep space ranging are definedand compared: two-way ranging from a node, two-way rangingfrom a user, one-way broadcast ranging, and one-way point-topoint ranging. Tradeoffs in accuracy, latency, and complexityare discussed. Pseudo-noise ranging approaches compatiblewith each measurement mode are identified and a link analysisis performed to assess measurement accuracy, determine userservice volumes, size relay hardware, and plan operationsstrategies. Idealized measurement assumptions are dispensedwith to develop the concept of a “deep space trilateration”algorithm, in which the measurement models incorporate signalpropagation time, the motion of nodes and users, and processingdelays, which are all non-negligible effects at deep spacedistances. A “deep space joint doppler and ranging” algorithmis also developed to assess the benefits of incorporating bothrange and doppler information into a navigation solution.The navigation merits of the deep space relay architecture werepreviously assessed with a dilution of precision (DOP) analysis.On its own, the DOP simulation captured the intrinsic geometricquality of the architecture for trilateration but did not fullycapture user-achievable positioning accuracy. This paperestimates user navigation performance with a more rigorousfilter-based simulation. The simulation implements the deepspace trilateration and joint doppler and ranging algorithms foreach measurement method and accounts for measurement,clock, and ephemeris errors. The accuracy and timeliness ofsimulated user position estimates are compared across eachnavigation method for a variety of inner solar system users.