Solar System Data Mules: Analysis for Mars and Jupiter

This paper explores the ability to ferry data between Mars and Earth, and Jupiter and Earth, using a network of small spacecraft (termed “data mules”) placed in phase-shifted cycler orbits between both planets. These cycler orbits enable the data mules to periodically visit the destination planet without requiring large amounts of fuel. However, their long periodicity also limits the cadence of visits since several years may elapse between consecutive data mule flybys. To increase total data return to Earth, we compare two alternative concepts of operations. First, we assume that each data mule carries an optical terminal capable of establishing a very high-rate inter-satellite link with a spacecraft orbiting Mars and Jupiter (where all data to be returned is stored). This inter-satellite link operates for a short period of time, nominally during 1 day around closest approach of the data mule to the planetary body of interest. This is compared to normal Deep Space Network (DSN) operations, in which we optimistically assume a continuous direct-to-Earth link with a ground antenna. Through our analysis, we show that the concept of data mules can substantially increase the total amount of data returnable from planetary bodies when used as a complement to current DSN support. We also show how the system performance, measured in terms of total returnable data volume or amortized yearly data rate, depends on technological constraints to implement the deep space and proximity links, as well as geometrical constraints imposed by cycler orbits and the solar system.